4. You are packing clothes for vacation and don't want to take any t-shirts. You randomly choose 3 shirts from a drawer containing 4 t-shirts, 3 polo shirts, and 3 button-downs.
a. What is the probability that the first 3 shirts are t-shirts when you replace each shirt before choosing the next one?
b. What is the probability that the first 3 shirts are t-shirts when you do not replace each shirt before choosing the next one?
*I know this is a lot, but it would really help me out if someone could help me out, I don't know how to describe it, but thanks.*