Carla has $300 in her bank account. Each time she goes to the ATM, she withdraws $20. The amount of money left in her bank account after ATM withdrawals is represented by the function f(x)=300-20x. What does the -intercept represent?
A. After 15 withdrawals, Carla has $0 left in her account.
B. After 20 withdrawals, Carla has $0 left in her account.
C. After 20 withdrawals, Carla has $15 left in her account.
D. After 0 withdrawals, Carla has $300 left in her account.