please show workings

1. Dan buys and sells puff-puff. He sells each plate of puff-puff at 12 and buys at 5. Puff-puff has to be sold warm and cannot be reheated. The market is very uncertain but Dan is an optimist and believes the best will always happen. He knows that on a good day he can sell as much as 3.000 plates, on an average day he can sell as much as 1,000 plates and on a bad day he sells only 15 plates. What will be the net margin if it turns out to be a bad day