The time required (in s) to reach the final temperature is ______

Question

A steel ball of 10 mm diameter t 1000 K is required to be cooled to 350 K by immersing it in a water environment at 300 K. the convective heat transfer coefficient is 1000 W/m²-K. Thermal conductivity of steel is 40 W/m-K. The time constant for the cooling process t is 16s. The time required (in s) to reach the final temperature is _________