1. 30% of the population is rich, and the other 70% is poor. Among the rich, 40% uses iPhone and60% uses Samsung Galaxy. Among the poor, 50% uses iPhone and 50% uses Samsung Galaxy. If you saw a random person on the street playing with an iPhone, how likely is he/she rich?
2. X and Y are two independent random variables. We know that E(X) =80, Var(X) =144, E(Y) =12, and Var(Y) =9. Calculate the mean and standard deviations of the following functions of random variables: (a)X20 (b)0.5Y (c)X+Y (d)XY