DETROIT--Ford Motor Co. has increased cash rebates on the F-150 pickup by $500 to $2,500 to cut inventories of unsold vehicles, a spokesman told Reuters Thursday. The rebate is specific to the F-150 regular cab pickup, and will only be available through the Memorial Day holiday weekend, Reuters reported. Large incentives are expected to increase vehicle sales about 4 percent for the month to a seasonally adjusted annual rate of 17.0 million or more, analysts told Reuters.