Future value.   A speculator has purchased land along the southern Oregon coast. He has taken a loan with the​ end-of-year payments of ​$7 comma 000 for 8 years. The loan rate is 5 ​%. At the end of 8 ​years, he believes that he can sell the land for ​$50 comma 000 . If he is correct on the future​ price, did he make a wise​ investment?

You are thinking of making your mansion more energy efficient by replacing some of the light bulbs with compact fluorescent bulbs, and insulating part or all of your exterior walls. each compact fluorescent light bulb costs $4 and saves you an average of $2 per year in energy costs, and each square foot of wall insulation costs $1 and saves you an average of $0.20 per year in energy costs.† your mansion has 150 light fittings and 3000 sq ft of uninsulated exterior wall. to impress your friends, you would like to spend as much as possible, but save no more than $750 per year in energy costs (you are proud of your large utility bills). how many compact fluorescent light bulbs and how many square feet of insulation should you purchase? how much will you save in energy costs per year? (if an answer does not exist, enter dne.)