Solve the following problem:
Problem: Converting sunlight to electricity with solar cells has an efficiency of 15%. It's possible to achieve a higher efficiency (though currently at higher cost) by using concentrated sunlight as the hot reservoir of a heat engine. Each dish in the figure concentrates sunlight on one side of a heat engine, producing a hot-reservoir temperature of 490 degrees C. The cold reservoir, ambient air, is approximately 28 degrees C. The actual working efficiency of this device is 30%.
Part A: What is the theoretical maximum efficiency?
Please show all work and steps to determine the theoretical maximum efficiency.