for the power question all designs end up providing 100MW
A losses 20MW
B you find I= V/R= 508000/40=12700, Then use power loss equation and you get ~4MW
C is only 30kW*100= 3MW
so C would be the most efficient
hate to tell this but 20 isnt B its A, coz when u calculate the energy of the 10um wavelength you get 0.13, thats lower than B which is 0.17
so the human body wavelength which is around 0.13 would not have enough energy to create a photoelectric thing in B, making the detector useless
i hope...