General Motors to Rebate $200â$500 on Small Cars
GM chmn Thomas A Murphy says rebates ranging from $200 to $500 will be paid to customers who bought or who will buy any of co's compact and subcompact models between Jan 13 and Feb 28; action follows similar moves by Ford and Chrysler; spokesmen for both cos say sales have increased since rebate program began; incentive plans designed to stimulate car sales continue to proliferate outside auto indus; at least 35 cos, many in Detroit area, are paying rebates to their employes; Amer Motors and Chrysler are cooperating by contributing to such rebates, which range up to $300; Sperry & Hutchinson Co will give 50,000 S & H Green Stamps to its employes who buy new car before Mar 31, and Gulf & Western Industries is offering $100 bonus (M)