23) The lead time plus the safety-stock time will be the reorder point, so 13+5 = 18 days' usage. That will be (18/45)·(9810 spools) = 3924 spools
You can figure the number of spools per day and for 5 days and for 13 days, but that seems like extra work.
24) The reorder point is 150 -40 = 110 units below the opening balance. When the sum of QtyOut-QtyIn exceeds 110, the reorder point has been reached. The January change in balance is 100 -30 = 70; the February change in balance is 20 -40 = -20, so is 50 when added to January. The March change in balance is 80 -10 = 70, so totals 50+70=120 when added to January and February. That is, the reorder point will have been reached in March.
If you want to fill in Number on Hand, it will be 150 -70 = 80 in Jan; 80 -(-20) = 100 in Feb; and 100 -70 = 30 in March, which is below the reorder point of 40.
25) The first 100 shredders cost 100·$31.90 = $3190. The next 50 cost 50·$30.89 = $1544.50. The remaining 50 of the 200 sold cost 50·$31.75 = $1587.50. The cost of goods sold was
... $3190 +1544.50 +1587.50 = $6322.00 . . . . . . matches the 2nd selection
