题目内容：

英语翻译
payam is an automobile manufacturer that specializes in production of an economy model and a midsize model.the price of the economy model in market is $15,000 and the price of midsize model is $25,000.payam has one production plant for both.1200 labour hours per day are available in this plant.production of the economy model requires 20 labour hours per car and production of the midsize requires 40 labour hours per car.also the total daily demand for car is 40.sales manager of payam wants to allocate car production to maximize daily revenue.
a,write down your optimization problem.
b,solve the problem graphically.what is the solution?
c,solve the problem with SOLVER and report the shadow prices for each constraint.