Consider a gas turbine that has a pressure ratio of 6 and operates on the Brayton cycle with regeneration between the temperature limits of 20 and 9008C. If the specific heat ratio of the working fluid is 1.3, the highest thermal efficiency this gas turbine can have is
(a) 38 percent
(b) 46 percent
(c) 62 percent
(d) 58 percent
(e) 97 percent