MythosHF

Use your financial calculator to calculate the MIRR.

It is the rate the equate the PV of Cash Outflows with the FV of Cash Inflows, MIRR also assumes that the cash flows are reinvested at the firm's WACC( one of the reason it is superior to the IRR which assumes it is reinvested at the IRR).

So,

Using your Financial Calculator:
Input PV : using cost of capital( as given) as discount rate
Input FV: Calculated using using cost of capital as required rate of return
Input N
CPT I/Y for the MIRR

Hope this helps!