How come it seems like we find two different values for both $M_{-}C$ and $M_{-}B$ and add them together to find $M_{-}C.$ I am

confused why there is M$\_$C found by rf above in the picture and then $($r$\_$BA X R$\_$B$).$ I am confused because it feels like we are

finding M$\_$c two differnt ways but they are two different values. Could you please explain the difference of what and why for

those two values and explain the M$\_$A equation? I attached a cheg solution. For pulley at B:

Resultant force at $B,R_B=\{145(-cos20j+sin20k)-(215j)\}N$

$R_B=\{-351\mathrm{.}25j+49\mathrm{.}59k\}N$

Resultant couple at $B,M_B=\{(-215+145)(0\mathrm{.}075)i\}N-m$

$M_B=\{-5\mathrm{.}25i\}N-m$

For pulley at C :

Resultant force at $C,R_c=\{(155+240)(-sin10j-cos10k)\}N$

$R_c=\{-68\mathrm{.}59j-389k\}N$

Resultant couple at i Thanks!