I am looking at purchasing a portfolio of vehicle leases with known payment schedules and residuals. The payments on different vehicles vary from 3 months to 40 months in term and I can calculate the monthly total. When the vehicles come off lease, I can also calculate and include in the stream of payments the guaranteed residual values. The discount is fixed at 15%. Is there a way that I can calculate the NPV and IRR using a given reinvestment rate, say 3% and known payments throughout the contract and total value of the payments and payment dates?

Thank you for your help. I am new to this forum but want to extend my thanks for all and any support.