please show me the formula

Chapter 6 Exercise 17 17. Charles McKeown is an acquisitions editor for a college textbook publisher. The file Books.xlsx that accompanies this book contains a list of 151 textbooks that Charles has an opportunity to acquire from another publisher. For each title, the file lists the price acquisition cost) and net present value of expected future sales. Assume that Charles may select up to 20 tiles from this list and spend $12 million on these acquisitions. a. Create an optimization model in a spreadsheet to solver Charles' problem. b. Which titles should Charles acquire, how much of the budget would be used, and what is the expected NPV of these titles