Lead shot may be manufactured by dropping molten-lead droplets into water.Assuming that the droplets have the properties of solid lead at 300◦C, calculate the time for the center temperature to reach...

Lead shot may be manufactured by dropping molten-lead droplets into water.Assuming
that the droplets have the properties of solid lead at 300◦C, calculate the time
for the center temperature to reach 120◦C when the water is at 100◦C with h=
5000 W/m2 · ◦C, d =1.5 mm.