Hi, I'm stuck on these questions. I was wondering if I can get some help please!

Let X be a random variable with exponential distribution with mean 1

1.(i) Write the p.d.f. for the random variable X.

(ii) P(X > 4|X > 2).

(iii) P(X > + ) where = E(X) and 2 = V ar(X).

(iv) Find P(X x) = F(x)