You are interested in determining the optimal stock level of designer shoes that you would like to order from the manufacturer based on the estimated demand, with a mean of 125 and a standard deviation of 5 (normally distributed). The purchasing cost is 120 SAR per pair, while you sell the same at 190 SAR per pair. You plan to sell the stock in 3 months, the remaining stocks that are not sold by the end of 3 months are offered on sale at a price of 105 SAR per pair to dispose the stocks.