An item initially valued at 100$ goes down in value by 20% the first year then goes up in value 10% the second year and goes down again by 20% in the third year. what is the value of the item at the end of the third year

The john deere company has found that revenue,in dollars, from sales of heavy-duty tractors is a function of the unit price p, in dollars, that it charges. if therevenue r is r(p)= -1/2p^2 +1900pa)how much revenue will the company generate if they sell 700 tractors? b) how many tractors does the company want to sell to maximize the revenue?