0.05+1.15(rm-rRF)=0.12
1.15(rm-rRF)=0.12-0.05
1.15(rm-rRF)=0.07
r m - r R F=0.07/1.15
r m - r R F= 7 / 115
You cannot solve thies equation because there are 3 unknowns.....
So I do not know what you want us to do with it ????
