A topic that never took up too much of my time in the past has suddenly become of great importance to me. Until I took over The Washington Post's annual campaign for Children's Hospital, I never gave much thought to the many ways to which people raise money for charity.

One of the best methods is familiar to most District Liners. It's the idea of one big "community" greeting card signed by everybody in the office instead of multiple intramural mailings. Money saved by not exchanging cards with colleagues is diverted to Children's Hospital.

I found myself wondering just how much money this plan could realize in a typical office.

To get some facts, I went to a neighborhood drug store and priced Christmas cards. Four differnt kinds were on display. The least expensive was $1.79 for 32 cards. The others were 16 cards for $1.49, 18 for $1.99, and 20 cards for $3.29.

I decided to calculate an average cost per card and apply the results to my theoretical office. What emerged was an average cost of about 10 cents per card. You can spend less. Ou can also spend a lot more -- and many people do.

Next, I had to pick an office size. For the sake of simplicity, 20 seemed to be a good number. If each person in an office with 20 employees mails a greeting card to 19 colleagues, 380 cards will be exchanged. Multiply 380 by 10 cents. Then multiply 380 times the 15 cents it costs to mail letters these days.

I found that the cost of the cards would be $38.00 and the cost of the postage would be $57.00. The Two together would come to $95.00.

If every envelope that came to me for Children's Hospital contained $95.00, we could knock off that "builtin deficit" in short order and perhaps even get a head start on the operating deficit for next year.

That isn't possible, of course, but every dollar helps. Our little exercise in multiplication demostrates how much is spent on intramural cards exchanged among only 20 colleagues. If there are 50 people in your department, 2,450 cards and 2,450 15-cent stamps would be involved, and the expenditure would be $612.50. That ain't hay.

As Mr. Nixon used to say, let me make one thing perfectly clear. I am not suggesting that we abandon the fine old custom of exchanging holiday cards with friends and relatives, especially those we see infrequently. It's the colleagues you see at work every day who don't need to be greeted through the mails. A handshake and personally expressed good wishes are just as good -- and perhaps better.

One reader who received a chain letter based on a mailing of 20 copies used a similar method to determine the cost of keeping the chain going and came up with $7.20. She cussed out the prepetrator and mailed us the money. Ah, how I wish that others who received that chain letter had thought to do likewise!

Six organizations sent money to be tallied in this day's report. Employees of the West Heating Plant, faithful friends of the hospital for many years, contributed $20. Members of the Committee on Democratic Education chipped in $25. I trust their gift touches of some partisan rivalry that will result in a suitable Republican response. and then a rebuttal from the Democrats.

Two groups sent in money that accumulated in their coffee funds. The guys and gals at the General Services Administration, Region 3, Finance Division came up with a healthy $62.02. Not to be outdone, the Army Mutual Aid Association contributed its $75.34 profit to the children. We sure do drink a lot of coffee in Our Town, don't we?

The Heckman Family Foundation found time to "distribute funds again" and moved us into three-digit territory with a gift of $100.

The final group in today's report sent a letter which must be quoted in its entirety: "Here's a start for next year's Children's Hospital campaign from an anonymous club which has disbanded." The envelope contained a check for $261.90. I'm left to marvel at the good deeds this nameless group must have done when it existed.

Our six group donors combined to add $544.26 to the shoebox. Thirteen individuals gifts brought in $174.20, so our total for today is $718.46. We began the day with $1,636.78, so our total to date rises to $2,355.24.

We're just going to have to do better. The drive is already six days old there are only 56 more mailing days until our drive ends on Jan. 31. At this rate we're not going to collect enough to pay for more than a couple of tonsillectomies. Help!

Perhaps if I post my mailing address again it will help get some unmailed letters into mailboxes. Please make your tax deductible checks to the order of Children's Hospital and mail them to: Scott Chase, c/o The Washington Post, 1150 15th St. NW, Washington, D.C. 20071.