大概懂题意 但是不知怎麽用微积分思考 帮忙一下了 1.A toy manufacturer estimates the demand for a game to be 2000 per year. Each game cost$3 to manufacture,plus setup costs of $500 for each production run. If a game can be stores for a year for cost of $2, how many should be manufactured at a time and how many production runs should be minimize costs? 2.An oil well generates a continuous stream of income of 60t thousand dollars per year, where t is the number of years that the rig has been in operation . Find the present value of this stream of income over the first 20 years at a continuous interest rate of 5%. 3.A company manufactures two products, in quantities x and y. Because of limited materials and capital, the quantities produced must satisfy the constraint 2x^2+5y^2<=32500. If the company's profit function is p(x,y)=4x+5y dollars. a. How many of each product should be made to maximize Profit? Also find the maximum profit. b. If the material and capital have chance to increase, which means the production constraint may change to 2x^2+5y^2<=(32500+h),estimate every unit change of h will result how many profit 拜托各位了 实在是不习惯这种应用题 --

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