12. An open-topped storage box with a square base has a capacity of 5 m3. The material for the sides costs $1.60/m?2 while the material for the bottom costs $2.00/m2. Find the dimensions that will minimize the cost of making the box. [5 marks] 13. An apple orchard has 2000 trees per hectare and the average yield is 300 apples per tree. For each additional tree planted per hectare the average yield per tree is reduced by about 0.1 apple. How many trees per hectare will give the largest crop of apples? [4 marks] 14. An isolated farm house is located on the bank of a straight canal that is 200 m wide. Electric power for the house must come from a connection that is on the opposite side of the canal, 500 m downstream. If the cost to lay cable underwater is three times the cost of laying on land, what path should be chosen to minimize cost? [6 marks]