I need assistance figuring out the second part of this question:

Duck, an accrual basis corporation, sponsored a rock concert on December 29, 2017. Gross receipts were $300,000. The following expenses were incurred and paid as indicated:

Expense Payment Date

Rental of coliseum $25,000 December 21, 2017

Cost of goods sold:

Food 30,000 December 30, 2017

Souvenirs 60,000 December 30, 2017

Performers 100,000 January 5, 2018

Cleaning of coliseum 10,000 February 1, 2018

b)Using the present value tables in Appendix G, what is the true cost to Duck if it had to defer the $100,000 deduction for the performers until 2018? Assume a 5% discount rate and a 25% marginal rate in 2017 and 2018.

I'm not looking for the straight out answer, but steps in how to solve this on my own, or an example of how to solve it. I'm stuck and can't find and example in my book that would help.