If the marginal benefit of the first donut is 30 , the marginal benefit of the second donut is 15, and the marginal benefit of the third donut is 10, what is the total benefit from eating 2 donuts?

Mr. pines is considering buying a house and renting it to students. the yearly operating costs are $1,900. the house can be sold for $175,000 at the end of 10 years and it is considered 18% to be a suitable annual effective interest rate. if the house costs $100,000 to purchase, how much would you need to charge your tenants each year in rent? (assume a single payment for the years rent at the end of each year)