A metal ball of diameter 60 mm is initially at 220⁰C. The ball is suddenly cooled by an air jet of 20^o C. The heat transfer coefficient is 200 W/m².K. The specific heat of metal, thermal conductivity and density of the metal ball are 400 J/kg.K, 400 W/m K and 9000 kg/m³ , respectively.

The ball temperature (in ^oC) after 90 seconds will be approximately