3)Let T1, T2, . . . , Tn be a random sample from the shifted exponential distribution with
R(t) = exp[-(t - (theta))/70], t > theta.

(a) Show that n(T(1) - (theta))/70 has the exponential distribution with mean one, where T(1) = min{T1, T2, . . . , Tn}.
(b) From part (a), what is a 90% confidence interval for theta?