Consider the Following to Answer the Question(s) Below

Consider the following to answer the question(s) below:
The owner of a small convenience store is trying to decide whether to discontinue selling magazines. He suspects that only 5% of the customers buy magazines and thinks that he might be able to sell something more profitable. Before making a final decision, he keeps track of the number of customers who buy magazines each day. On a typical day he has 280 customers in his store.
-On a typical day, what would be the standard deviation of the number of customers who buy magazines?

A) 3.65
B) 14
C) 13.32
D) 25
E) 5