John and Tau take their toys down to a nearby pond to play. John has a toy boat made from wood. He places the wooden boat on the pond and it floats. Tau, being a cheeky little boy, wants to make John’s wooden boat sink. So he attaches a piece of lead on one end of the string, and ties the other loose end onto John’s boat and gently places the lead into the water. Determine the smallest amount of lead (mass) that will be enough to sink John’s boat, assuming the specific gravity of wood is 0.5 and the density of the pond water is equal to the density of pure water.