What is the overall efficiency for conversion of sunlight to electricity via biomass and coal as intermediates?

It's been estimated that the efficiency of conversion of the energy in sunlight to energy stored in the chemical bonds of the products of photosynthesis (in biomass) is about 4%. Assume that 2% of accumulated biomass eventually winds up being converted to coal. The efficiency of a reasonably typical pulverized-coal-fired power plant, in terms of conversion of the chemical energy in the coal to electricity leaving the plant to consumers, is 35%. (a) What is the overall efficiency for conversion of sunlight to electricity via biomass and coal as intermediates? (Notice that we have not taken into account energy requirements for mining and transporting the coal.) (b) Look up the efficiency of conversion of sunlight into electricity in a silicon photovoltaic cell. (c) Compare your answers to a and b and comment on the comparison