A heat engine takes heat QH from a hot reservoir and uses part of this energy to perform work W. Assuming that QH cannot be changed, how can the efficiency of the engine be improved?
(a) Increase the work W; the heat QC rejected to the cold reservoir increases as a result.
(b) Increase the work W; the heat QC rejected to the cold reservoir remains unchanged.
(c) Increase the work W; the heat QC rejected to the cold reservoir decreases as a result.
(d) Decrease the work W; the heat QC rejected to the cold reservoir remains unchanged. (e) Decrease the work W; the heat QC rejected to the cold reservoir decreases as a result.