Bh 7.33) alice walks into a post office with 2 clerks. both clerks are in the midstof serving customers, but alice is next in line. the clerk on the left takes an expo(λ1)time to serve a customer, and the clerk on the right takes an expo(λ2) time to serve acustomer. lettbe the amount of time alice has to wait until it is her turn.(a) write down expressions for the mean and variance oft, in terms of double integrals(which you do not need to ) find the distribution, mean, and variance oft, without using calculus.