Based on the context and the answer, generate a question. 

Context: There is a room full of vending machines . I had a 20 dollar bill and I wanted a Coke Zero . In a quiet hour , I walked down to the emergency department and asked the clerk if there was a cashier anywhere who took payments at night , so I could get change . He sent me to the security desk , staffed by a VA police officer who told me that there was no cashier anywhere , and no change machine he could think of .

Answer:

They wanted to buy themselves a snack .



Why did the narrator need to get change ?