The answer is $1644.
she make 12 visits with a co-payment of $15. 15x12 = 180
305 x 12 = 3660 (total cost of all appointments)
3660 x .40 = $1464 (total cost times her 40%)
$1464 + $180 = $1644 (you must add co-payment to total cost)
You can always draw a right-angled triangle where the sloped side c is the line between the two points of interest, and a and b are the sizes of the horizontal and vertical lines.