Oscar's T-shirt Shop charges a design fee of $25 plus $15 per shirt for each new order. If Oscar charges the cost per shirt to $20, which of the following representations would accurately describe the situation? I. The difference between the rate of change for the new cost structure and rate of change for the old cost structure is $5 per shirt. II. The equation y=25x+20 represents the relationship between the total cost of the order, y, and the number of shirts, x, in the new cost structure. III.