A certain manufacturer of cake, muffin and bread mixes has 100 buyers of whom 50 purchase cake mix 40 purchase muffin mix and 20 purchase both cake mix and muffin mix. if a buyer is to be selected at random from the 100 buyers what is the probability that the buyer selected will be one who purchases neither cake mix nor muffin mix?

A. 1/10
B. 3/10
C. 1/2
D. 7/10
E. 9/10