Consider the Following Three Applications of Fuel Cells for Producing $\mathrm { CO } _ { 2 }$

Consider the following three applications of fuel cells for producing electricity to power a vehicle.
(i) A proton exchange membrane fuel cell uses hydrogen produced by electrolysis using electricity generated by burning coal.
(ii) A proton exchange membrane fuel cell uses hydrogen produced by electrolysis using electricity generated by a photovoltaic array.
(iii) A solid oxide fuel cell uses methane as a fuel.
For each case discuss as quantitatively as possible
(a) The overall efficiency of converting primary energy to energy at the vehicle's wheels
(b) The $\mathrm { CO } _ { 2 }$ emissions per $\mathrm { MJ }$ of energy at the vehicle's wheels