You are a restaurant manager. You must pick 15 entrees for your menu. There are 18 meat offerings and 10 poultry offerings to choose from.

a)In how many ways can 15 entrees be randomly selected out of the 28 meat and poultry offerings?

b)In how many ways can 15 entrees be chosen, if 9 must be meat and 6 must be poultry?

c)If 15 entrees are randomly selected from the 28 offerings, what is the probability that 9 are meat and 6 are poultry?

please show work. trying to learn. thank you