Answer:
(a) The graph is shown below.
(b) Domain : [0,90]
(c) Origin represents the initial position of the truck.
Explanation:
(a) Let no. of miles be y and no. of gallons be x. Then, initially x=0 and y=0 and when x=90 then y=660 . The equation of this determined by formula:

So the corresponding graph for this equation is given below :
(b) Domain : [0,90]
(c) Origin represents the initial position of truck when no. of gallons used is 0 and no. of miles covered is 0