probability density function

hello, first time poster here

I have this homework and I'm stuck in a question, heres the following:

rational formla for peak flow: Q=CIA

C= runoff coefficient

I= averge rainfall inensity

A= drainage are

th pdf of I is:

f(i)=2/3 e^(-2/3), i>=0

At the shopping bypass channel the depth of flow is:

h=KQ^0.6

^means exponent

so questions:

a) Find the comulative dist. F (i) DONE

b) Prove f(i) is a pdf DONE

c) Find the pdf and the comulative distribution of peak runoff Q: f(q) and F(q)

d) Find the pdf and comulative distribtion of teh depth of pea flow in the bypass

e) if C=200 and A=60, find the probability that th peak runoff from a storm is between 2,900 and 4,000

Now, I alread did a) and b) and I know how to do e), but I just can't figure out how to do d) and e)... I was thinking just substituting I into the equation for Q... but I don't think that's right...

any ideas??