Truncated prior distribution

Can anyone show me how to set out this problem so i can tackle it myself?

Suppose that a random sample of size n = 100 from an exponential distribution with parameter $\displaystyle \theta$ is about to be collected. It is thought that a Ga(2, 2) prior distribution for $\displaystyle \theta$ is appropriate but, since it is believed that values of $\displaystyle \theta$ exceeding 6 are impossible, the prior distribution is truncated above 6.

Calculate the prior probability that $\displaystyle \theta$ exceeds 6 assuming the truncated prior distribution. What is the probability when the prior distribution is not truncated?

Thanks!