Answer:
the ratio of the heat rejected to the cold reservoir for the improved engine to that for the original engine is 0.68
Explanation:
Given information
initial efficiency, η[tex]_{1}[/tex] = 0.28
final efficiency, η[tex]_{2}[/tex] = 0.51
ratio of the heat rejected = (1 - η[tex]_{2}[/tex])/(1 - η[tex]_{1}[/tex])
= (1 - 0.51)/(1 - 0.28)
= 0.68