MIRR discount rate

Hello, I have an exercise in which I need to calculate IRR & MIRR. While calculating IRR I used 10% & 15% to end up with IRR of, let's say 13%. Which rate I should use to calculate MIRR with help of standard MIRR equation: [PVR/PVI]*1/n*(1+r)-1 ...and if it is IRR, I assume that I must calculate PV of inflows/outflows with that rate as well...correct? Thank you in advance for your help! Regards, PJ