Answer:
Missing word "b. What is the reorder point? c. How often should an order be placed?"
a. Optimal order quantity (EOQ) = (2AC/C)^(1/2). A=21840(420*52), O=20, C=0.5
Optimal order quantity (EOQ) = (2*21840*20/0.5))^(1/2)
Optimal order quantity (EOQ) = 1321.816931
Optimal order quantity (EOQ) = 1321.81 units
b. Reorder point = (420/7)*4
Reorder point = 60 * 4
Reorder point = 240 units
c. Time = 365*EOQ/A
Time = 365*1322/21840
Time = 22.0938645
Time = 22 days