More and more shoppers prefer to do their holiday shopping online from companies such as Amazon. Suppose we have a group of 10 shoppers; 7 prefer to do their holiday  hopping online and 3 prefer to do their holiday shopping in stores. A random sample of 3 of these 10 shoppers is selected for a more in-depth study of how the economy has impacted their shopping behavior.

a. What is the probability that exactly 2 prefer shopping online?

b. What is the probability that the majority (either 2 or 3) prefer shopping online?