Briefly describe the difference between classical estimation approach and Bayes esti- mation approach. Describe how to combine the prior distribution and sample obser vations to get a posterior distribution. [1+2] Let Y1, . . . , Yn be iid Poisson(x10), where the values ; are known positive values of an explanatory variable, x, and 0 is the unknown parameter of interest. Let 0 have a gamma(a, B,) distribution. (a) Find the posterior distribution of 0. (b) Calculate the posterior mean and variance. [10]