Since they are currently sold for 200 and give a contribution of 40, the cost must be 200 – 40 = 160. They are going to increase the price to 280 and so the new contribution will be 280 – 160 = 120 per unit.
So, using the US inflation rate of 3%, the contribution at time 1 = 150 x 120 x 1.03 = 18540
At time 2 = 480 x 120 x 1.03^2 = 61108, and so on.