There's a lot of talk these days about switching to such coffee substitutes as tea and cocoa. But not much is said about the caffeine "kick" these drinks may or may not have.

What you use as a coffee substitute depends a lot on why you drink coffee. For the majority of coffee drinkers, a good cup of the black brew is needed in the morning or after lunch as a "lift." The smell of coffee and the flavor count, but the big thing for coffee drinkers is the caffeine jolt to the central nervous system.

So, if you're trying to switch to something else for a pick-me-up, it must have a stimulant. Tea might be your best bet. It has about half the amount of caffeine as a cup of ground roasted and about a third less than a cup of instant coffee.

But tea is much cheaper than coffee. In my area, I found that tea costs 1.4 cents a cup if you use store brand tea bags, compared with 2.4 cents a cup for instant coffee and up to 6.5 cents a cup for ground-roasted coffee.

If you drink two cups of tea, you'll get the same amount of caffeine as you get in one cup of ground-roasted coffee and a good deal more than you get in one cup of instant coffee.

But you must use tea bags or loose tea. Instant tea has from one-third to one-half less caffeine in it than these nonprocessed teas.

By drinking two cups of tea instead of one cup of coffee, you get a good lift, you get more water and more warming effect. And you get all this for less money than the same lift you'd get from coffee.

So much for tea. Now, let's look at cocoa.

Nobody expects a coffee drinker to completely substitute cocoa for the black brew. But some coffee drinkers are switching, say, one cup a day with cocoa.

Cocoa has only a fraction ofthe caffeine coffee and tea contain but it also has another stimulant called theobromine which is milder than caffeine. Together, they can give you a bit of a lift.

Actually, pure cocoa from Bahia, Brazil, contains the same amount of caffeine as a good stiff cup of tea. Cocoa from Accra, Africa, contains far less caffeine. The trouble is, cocoa manufacturers in this country mix the different raw products and you never really know how much caffeine you're getting. They don't have to label it because it's not an additive.

Cocoa is more of a food. It has some fat, carbohydrates and, when you mix it with milk (which you must do to make it taste right) it has a good slug of protein. If you use instant cocoa powders that have nonfat, dry milk mixed in and use hot skim milk instead of water, you get an even bigger blast of protein.

But, what about the decaffeinated-coffee drinkers? The best bet for a switch drink is probably Postum. It's a coffee-flavored concoction that costs considerably less than ground coffee per cup and about a third less than decaffeinated instant coffee.

Postum also has some nutritional value because it has a cereal base. Coffee has no nutritional value. The taste of Postum used to turn some decaffeinated-coffee drinkers off, but the manufacturer has improved the flavoring considerably and some coffee drinkers say it's not bad now.

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Q. Is it necessary to be represented by an agent to submit written work to publishers and TV producers? If so, how can I get in touch with a reputable agent? I'd also like the government address where I can submit material for copyright to prevent plagiarism. - B.W., Farmington Hills, Mich.

A. Unless you have a good contact with a publisher or producer, it's best to be represented by an agent. The Broadcasting Yearbook, available at most libraries, has lots of information on this subject, including a list of reputable agents. Libraries also have other writers' guide books that list agents.

Only published works can be copyrighted. As long as your writing is in the idea or draft stage, it can't be copyrighted. You can send yourself a copy of your work through certified mail (unopened) which can serve as dated evidence. You do have protection against plagiarism through common law and "unfair business practices." For more information on what can be copyrighted and how, write: Copyright Office; Library of Congress, Washington, D.C. 20559.

Q. You recently wrote about a man who put on a new coat of paint and it wouldn't stick to his house. You didn't mention the fact that acrylic (latex) paint won't stick to an old coat of oil paint without using a prime. - J.B., Whittier, Calif.

A. You are in error but it's a common error that some painters share. It's controversial but experts say the most important element in using latex paint is surface preparation. If the surface is scrupulously clean, you can put latex on top of oil paint. Read the paint instructions carefully and follow them.