An adiabatic heat exchanger is used to heat liquid oil (c_p = 0.430 Btu/lbm*R) at 100 $^\circ$F entering at a rate of 3.9 lbm/s with hot air entering at 1100 $^\circ$F at a rate of 14.5 lbm/s. If the exit temperature of the oil is 900 $^\circ$F, then what is the exit temperature in $^\circ$F of the air?

Assume the following constant properties for air:

c_v = 0.185 Btu/lbm*R

c_p = 0.254 Btu/lbm*R

$^\circ$F