At the beach, gavin and his sister both built sandcastle and then measured their heights. gavins sandcastle was 3 7\3 feet tall and his sisters was 2 3\8 feet tall how much taller was gavins sandcastle than his sisters

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?