Can anyone else with this? i’m not looking for it to be fully rationalize.

Math question.. plz me .. best answer all

What is the gcf of 20c^3-5c^4+30c^6

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?