how to calculate efficiency of an air/air intercooler?

[chiller]

hi
im trying to calculate the efficieny of an air/air intercooler.
could someone kindly help me on this.

the hot air:
temp in: 60degC
temp out: -14degC

cold side:
temp in: -40 degC
temp out: 34degC

i found it to be 74%.
from
(60--14)=74
(60--40)=100

am i correct?

thanks for help.