The Power at Ice Station Lion is supplied via solar cells. Once a year, a plane flies in and sells solar cells at a price of $20 per cell. Because of uncertainty about future power needs, the ice station can only guess the number of cells that will be required during the coming year: No. of Cells 50 60 70 80 90 100 Probability 0.20 0.15 0.30 0.10 0.15 0.10 If the ice station runs out of solar cells, a special order must be placed at a cost of $30 per cell. How many cells should be ordered from the plane to minimize expected cost?