A tub is filled with water and a wooden cube \( 10 \, \text{cm} \times 10 \, \text{cm} \times 10 \, \text{cm} \) is placed in the water. The wooden cube is found to float on the water with a part of it submerged in water. When a metal coin is placed on the wooden cube, the submerged part is increased by \( 3.87 \, \text{cm} \). The mass of the metal coin is ______ gram. (Take water density as \( 1 \, \text{g}/\text{cm}^3 \) and density of wood as \( 0.4 \, \text{g}/\text{cm}^3 \))
