The convection coefficient for flow over a solid sphere may be determined by submerging the sphere, which is initially at 25 °C, into the flow, which is at 75 °C, and measuring its surface temperature at some time during the transient heating process. If the sphere has a diameter of 0.1 m, a thermal conductivity of 17 W/(m-K), and a thermal diffusivity of 0.60 x 105 m²/s, at what time will a surface temperature of 60 °C be recorded if the convection coefficient is 300 W/(m²K)