In (Q, R) system, we define n(R) as the expected number of stock-outs incurred in a cycle. Let p denote the penalty cost per unit of unsatisfied demand. λ is the demand mean per unit time and Q is the lot size (order quantity). The term pn(R)λ​/Q represents ___. a) the average annual cost b) the average setup cost per unit time c) the average shortage cost per unit time the d) total expected shortages cost per cycle