WASHINGTON President Bush on Wednesday signed a multibillion-dollar economic rescue package on Wednesday that means $300 to $1,200 rebates for many American households. Bush called the measure "a booster shot for our economy" to stave off a recession. Several dozen members of Congress, including House Speaker Nancy Pelosi, stood on the stage behind Bush as he signed the bill. Rebates are to go out beginning in May to taxpayers and low-income people, including seniors living off of Social Security and veterans who depend on disability checks. Businesses would get tax breaks for investing in new plants and equipment. Most taxpayers will receive a check of up to $600 for individuals and $1,200 for couples from the Internal Revenue Service, with an additional $300 per child. People earning at least $3,000 and those who owe little or no taxes would get $300 for singles, $600 for couples. Those making more than $75,000 and couples with income exceeding $150,000 are to get smaller rebates $50 less per $1,000 they make over those thresholds.