Which table shows a constant rate of change? a days 6 12 18 earnings ($) 225 450 750 b days 6 12 18 earnings ($) 225 500 750 c days 6 12 20 earnings ($) 225 450 675 d days 6 12 20 earnings ($) 225 450

1. according to the internal revenue service, the mean tax refund for the year 2007 was $2,708. assume the standard deviation is $650 and that the amounts refunded follow a normal probability distribution. a. what percent of the refunds are more than $3,000? b. what percent of the refunds are more than $3,000 but less than $4,000? c. what percent of the refunds are less than $2,000?