Farmers can get $8 per bushel for their potatoes on July 1, and after that, the price drops by 5 cents per bushel per day. On July 1, a farmer has 140 bushels of potatoes in the field and estimates that the crop is increasing at the rate of 1 bushel per day. Express the farmer’s revenue from the sale of the potatoes as a function of the time at which the crop is harvested, draw the graph, and estimate when the farmer should harvest the potatoes to maximize revenue.