Over the past few months. Kepfler and Associates have collected the following figures for demand of an electric transformer that they keep as a spare part for assembly equipment. Demand 1 2 3 4 5 6 7 S 9 10 % of months 50% 20% 10% 5% 5% 3% 3% 2% 1% 1% The cost of holding one transformer in stock for a month is JD 60. Any shortage of the part is estimated to cost JD 1,000 a unit a month. A. The probability of having demand that is less than or equal to 5 units is B. The best stock level for the transformer is units