Jen and Barry calculate the overall cost per shift y for "Jen & Barry's Fast Fresh Salad Bags". They determine that 20 salad bags can be produced for a total cost of $80 and that 50 salad bags can be produced for total cost of $125. Which of the following equations correctly models the total cost y per shift as a function of x salad bags produced per shift?
A. 3x + 2y = 220 B. 3x - 2y = 100 C. 2x + 3y = - 50 D. 3x - 2y = - 100