173. Let N denote the number of accident..-阿摩線上測驗
173. Let N denote the number of accidents occurring during one month on the northbound side
of a highway and let S denote the number occurring on the southbound side.
Suppose that N and S are jointly distributed as indicated in the table.
Calculate Var (N | N + S = 2).
(A) 0.48
(B) 0.55
(C) 0.67
(D) 0.91
(E) 1.25