In an ideal Brayton cycle with regeneration, air is compressed from 80 kPa and 108C to 400

Question:

In an ideal Brayton cycle with regeneration, air is compressed from 80 kPa and 108C to 400 kPa and 1758C, is heated to 4508C in the regenerator, and then further heated to 10008C before entering the turbine. Under cold-air-standard conditions, the effectiveness of the regenerator is
a) 33 percent
(b) 44 percent
(c) 62 percent
(d) 77 percent
(e) 89 percent