Exponential Distribution

Let X and Y be independent exponential random variables with parameters λ and µ. Let Z = min{X, Y }.
a. (3 pts) Find P(X = Z).
So for this I calculated P(X=Z)=P(X<Y) and got the answer (λ/λ+µ)
b.Find P(Z>z)
Can anyone help me with how to go about doing this part of the question. Thank you