I might be overthinking it but could someone double check my answer for the following question? It seemed to easy...and if they're wrong how do i calculate it?

Suppose that h is a secure hash that generates an n-bit hash value.

a) What is the expected number of hashes that must be computed to find one collision? 2^(n/2)

b) What is the expected number of hashes that must be computed to find 10 collisions? That is what is the expected number of hashes that must be computed to find pairs (xi, zi) with h(xi) = h(zi) for I = 0, 1, ,9? 2 ^(5n)

What is the expected number of hashes that must be computed to find m collisions? 2^nm