Required information [The following information applies to the questions displayed below.] DES Company manufactures folding chairs. Direct materials include hard plastic for the seat and back and metal beams for the legs. The standard cost sheet for a single chair includes the following direct materials information: Last month, DES purchased 26,100 sheets of hard plastic at a cost of $68,643. The company also purchased 52,700 metal beams at a cost of $76,415. DES produced 13,200 chairs. There was no beginning or ending inventory of plastic sheets or metal beams during the month. What are the advantages and disadvantages of computing total price and usage variances when there re multiple material inputs