A cash register contains only five dollar and twenty dollar bills. It contains fourtimes as many five dollar bills as twenty dollar bills and the total amount of money in the cash register is $640.

Let x be the number of five dollar bills and y be the number of twenty dollar bills.

A1) Write an equation using x and y modelling the part, "It contains fourtimes as many five dollar bills as twenty dollar bills."

A2) Write an equation using x and y modelling the part, "the total amount of money in the cash register is $640." See the notes on formatting dollars below.

A3) Find the total number of five dollar bills.

x=______five dollar bills