I’m not sure if this has been posted. Here is a way to calc MWRR with HP 12c.
V6, P133, Example 6.
g+CF0: 0.8 g+CFj: 0 g+Nj: 9 g+CFj: 1 g+CFj: 0 g+Nj: 19 g+CFj: -3 f+FV
This is not practical in the exam, since I made mistakes in Nj numbers for a few times. I won’t try it on 6/2.