Chapter 4, Problem 167P

An 18-cm-long, 16-cm-wide, and 12-cm-high hot iron block ${\text{(p = 7870 Kg/m}}^{\text{3}}{\text{, c}}_{\text{p}}\text{= 447 J/kg}\text{.K)}$ and initially at 20°C is placed in an oven for heat treatment. The heat transfer coefficient on the surface of the block is 100 Wm² K. If the temperature of the block must rise to 750°C in a 25-min period, the oven must be maintained at

(a) 750°C

(b) 830°C

(c) 875°C

(d) 910°C

(e) 1000°C