A type of extra-large SUV averages 12.2 miles per gallon (mpg) on the highway, but only 7.6 mpg in the city. What is the maximum distance, in miles, that this SUV could be driven on 21 gallons of gasoline?  Choose the correct choice from the following choices:
A) 190	B) 284.6	C) 300	D) 256	E) 312

Rationale: "so 12.2 * 21 = 256 . . imo option d is correct answer . ."
Answer: D