Hi, I have a question for which the answer is provided but I don't know how it is derived, could you help to explain it step by step please?

Thank you in advance!

A clothing store and a jeweler are located side by side in a shopping mall. If the clothing store spends C dollars on advertising and the jeweler spends J dollars on advertising, then the profits of the clothing store will be (42 + J)C - C2 and the profits of the jeweler will be (54 + C)J - 2/2. The clothing store gets to choose its amount of advertising first, knowing that the jeweler will find out how much the clothing store advertised before deciding how much to spend. The amount spent by the clothing store will be O 18.50. O 74. O 111. Correct! 37. O 55.50