You bought books from an online book store that charges a flat fee for shipping each order. There was no sales tax on this purchase. The graph shows the cost of purchasing x books. About how much did the books cost if the total purchase was $31.50?
A graph is shown in the xy-plane. The values on the x-axis ranges from 0 to 4 in increments of 1 and the values on the y-axis ranges from 0 to 30 in increments of 5. A line starts from a point around 3 decimal point 7 5 on the y-axis, goes up and passes through the point (2, 17 decimal point 5).

A.

$3.50
B.

$7.00
C.

$28.00