Please help Billy and Susie were saving up to buy the new Xbox. Billy got $50 for his birthday and saved $20 each week. Susie already had $25 and saved $40 each week. Write a system of equations to describe this situation.

The discrete random variables x and y take integer values with joint probability distribution given by f (x,y) = a(y−x+1) 0 ≤ x ≤ y ≤ 2 or =0 otherwise, where a is a constant. 1 tabulate the distribution and show that a = 0.1.2 find the marginal distributions of x and y. 3 calculate cov(x,y).4 state, giving a reason, whether x and y are independent. 5 calculate e(y|x = 1).