Here is a summary of the rules for gasoline purchases issued by the governors of Maryland and Virginia and the mayor of the District of Columbia.

The plan for Maryland has been in force since Thursday. The rules for Washington and Northern Virginia will go into effect tomorrow at 12:01 a.m.

Officials said the rules are designed to reduce lines at gasoline pumps by discouraging "tank-topping" and hoarding: MINIMUM PURCHASE

D.C. and Northern Virginia: $5 Maryland: $5 for four-cylinder vehicles; $7 for vehicles with six or eight cylinders. EXCEPTIONS

All area jurisdictions: No minimum for motorcycles or mopeds.

Maryland: No minimum for cars whose gas tanks hold eight gallons or less. CONTAINERS

All area jurisdictions: Maximum purchase of 2 gallons. PENALTIES

D.C.: None in mayor's order.

Virginia: Misdemeanor. Maximum $1,000 fine or 12 months in jail, but officials say heavy fines unlikely.

Maryland: Misdemeanor. Maximum $100 fine or 60 days in jail. Violators may be reported to state Motor Vehicle Administration, which can issue points for the violations after a heearing.

(Note: In Virginia, areas covered by governor's order are Arlington, Fairfax, Loudoun, and Prince William counties and cites of Alexandria, Falls Church, Fairfax City, Manassas and Manassas Park). CAPTION: Picture, no caption, By James M. Thresher - The Washington Post