Copper balls ( = 8933 kg/m 3 , k = 401 W/m K, c p =

Copper balls (ρ = 8933 kg/m³, k = 401 W/m · K, c_p = 385 J/kg·°C, α = 1.166 × 10^-4 m²/s) initially at 200°C are allowed to cool in air at 30°C for a period of 2 minutes. If the balls have a diameter of 2 cm and the heat transfer coefficient is 80 W/m² · K, the center temperature of the balls at the end of cooling is
(a) 104°C

(b) 87°C

(c) 198°C

(d) 126°C

(e) 152°C