If the emission, factor of producing electric power by PV cells is 100 g of CO2 per kWh, by wind power is 15 g of CO2 per kWh, and by coal is 1000 g of CO2 per kWh, then find the ratio of CO2 emission when
a) 15% of power comes from wind farms
b) 5% from a PV source, and
c) the rest from coal as opposed to when all power is supplied by coal-run power stations