A gas in a piston-cylinder undergoes a Carnot power cycle. The gas expands and compresses isothermally between two reservoirs at 600 K and 300 K. Determine a) the thermal efficiency, b) the percent change in the thermal efficiency if i) the hot reservoir is increased 20% while the cold remains the same K, ii) the cold reservoir decreases 20% while the hot remains the same and iii) if the hot reservoir increases 20% and the cold decreases 20%.