(a) Truck carries 90 gallons of diesel fuel to 660 miles.
So, 1 gallon of diesel fuel to 660/90 = 22/3 miles.
30 gallons of diesel fuel to = 220 miles.
Hence, if x-axis represents the number of miles and y-axis represents the number of gallons, then, (660, 90) and (220, 30) are points on the graph.
Join (660, 90) and (220, 30), we get the graph of a line.
Note that (0, 0) is also a point on the line.
Equation of the line is .
(b) x represents the number of miles. Therefore, the possible values for x is the closed interval [0, 660].
Hence, the domain of the function is [0, 660].
(c) Origin represents that the truck is not moving and there is no diesel fuel loaded in the truck.