Answer: b. Every 18 minutes, 28 more pizzas were set out on the buffet.
Step-by-step explanation:
The equation is in the form: y = mx + c
m is the gradient which represents the rate of change per a given value of x.
x here is every 9 minutes after 11:00. Every 18 minutes therefore will give x a value of 2 because 18/9 = 2.
The rate of change every 18 minutes is therefore;
= 14 * 2
= 28 pizzas