Poisson process - emergency call center question

Assume a Poisson process. An emergency call center gets 3 calls per minute average. What is the probability that the second call will come in 30 seconds and before 60 seconds have passed?

This is what I know for sure. Use two poisson variables X and Y and then add them together (maybe using moment generating function?)

X = time it takes for first call to come in

Y = time it takes for second call to come in

I'm not sure how to set up this problem and I guess I should use 3/2 as the poisson parameter? Thanks