QUESTION 18A tire shop changes about 4,250 tires per year, 14 percent of which are off-road tires. All off-road tires are purchased from an outside supplier at a cost of

$75 each. The shop uses a holding cost based on a 18 percent annual interest rate. The setup cost for placing an order is estimated to be $20.Determine the optimal time (in weeks) between placement of orders. (Round to two decimal places, and assume 52 weeks per year)