please solve it with a clear handwriting.

2) A particular power plant operates with a heat-source reservoir at 723.15K(450C) and a heat-sink reservoir at 343.15K(70C). It has a thermal efficiency equal to 75% of the Carnot-engine thermal efficiency for the same temperatures. (a) What is the thermal efficiency of the plant? (b) To what temperature must the heat-source reservoir be raised to increase the thermal efficiency of the plant to 45% ? Again is 75% of the Carnot-engine value