Retaining Wall - Resultant Location for sloping sliding surface

[CWEngineer]

Hi,

I am trying to figure out how to calculate the 7.79 ft resultant location in Example N-3 of EM 1110-2-2502 (please see attached document). I am calculating this value using a similar approach as if there was no key (will submit in subsequent thread), maybe this is where I am going wrong. I calculate a value of 9.14 ft. Not sure if the EM is wrong or I am missing something here. Really appreciate if your help in trying to figure this out.

Thanks

 

[CWEngineer]

Here are the hand calculations.