The campus bookstore wants to figure out the optimal number

of an operations management textbook to buy for the upcoming semester.

The cost and price is as follows:

Cost$/$unit $=$ $ $109\mathrm{.}00$

Selling price$/$unit $=$ $ $145\mathrm{.}50$

At the end of the semester, the leftover books can be sold back to the publisher

at cost less $10\%.$ That is$,$ they get $90\%$ of the cost back.