Show that Tad >1400K & find the ratio of secondary to primary airflow

Liquid n-butane at T 0, is sprayed into a gas turbine, as in Fig. P15.84, with primary air flowing at 1.0 MPa, 400 K, in a stoichiometric ratio. After complete combustion, the products are at the adiabatic flame temperature, which is too high, so secondary air at 1.0 MPa, 400 K, is added, with the resulting mixture being at 1400 K. Show that Tad > 1400 K and find the ratio of secondary to primary airflow.