'Let X1, X2, X3, and X4 be independent continuous random variables with a common pdf f(r) and edf F(z). Define Yi, Yz, Y3, and Y4 a5 Yi largest of Xi; "X4 Yz second largest of Xi,- X4 Ya third largest of Xi; ,X4 Y4 smallest of Xu X4 _ Find fyk (y) , the marginal pdf of Yk, for 1 < k < 4 Find E (Y2) _'