A computer dealer nds that the number of laptop computers he

A computer dealer nds that the number of laptop computers her dealership sells each day

is a random variable X where the probability distribution for X is given by

Pr(X = x) = {cx2/x! x = 1, 2, 3, 4, 5

{0 otherwise

where c is a constant. Determine

(A) The value of c

(B) Pr(X >= 3)

a) P(X=1)+P(X=2)+P(X=3)+P(X=4)+P(X=5)=1

c(1+ 4/2 + 9/6 + 16/24 + 25/120)=1

c=8/43

b)Pr(X >= 3)= P(X=3)+P(X=4)+P(X=5) = c (9/6 + 16/24 + 25/120) = 0.267