Question $1$

During the two hours of the morning rush from $8$ a$.$m$.$ to $10$ a$.$m$.,100$ customers per hour arrive at the coffee shop. The coffee shop has a capacity of $80$ customers per hour. What is the number of customers waiting at $10$ a$.$m$.$

A$.$

$40$

B$.$

$100$

C$.$

$20$

D$.$

$80$