Answer:
$108
Explanation:
1 box = $12
18 boxes = 12×18 = $216
Total = 18×65 = 1170 pens
Cost price, Cp = $216
3 = $1
378 = 378/3 = $126
1170-378= 792 pens remaining
4 = $1
792 = 792/4 = $198
Total selling price, sp = 126+198 = $324
Profit = Sp - Cp = 324 - 216 = $108