Aclassroom has 12 students with brown hair, 8 students with black hair, and 5 students with blonde hair. if three students are chosen at random, what is the probability that they all have black hair?

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?