The mileage from the Supermarket to the Library may be calculated using Pythagorean Theorem.
The coordinates of the Library are (7,10) and the coordinates of the Supermarket are (3,7).
So, the distance requested is √ [ (7-3)^2 + (10 - 7)^2 = √[ 4^2 + 3^2 = √ [16 + 9] =
= √25 = 5
So, he runs 5 miles.
And the reimbursement will be $0.50 / mile * 5 mile = $ 2.50.
Answer: option B) $ 2.50