When a body is kept in a fluid:
1. if the density of the body is greater than that of the fluid, it sinks.
2. if the density of the body is less, then it floats in the fluid.
when it floats on the surface of the fluid, it is at static equilibrium. In the vertical direction, there will be weight force acting downward and the buoyant force which will be acting upward. Since it is in equilibrium, the net force is 0. So the buoyant force must be equal to the weight of the material.
Buoyant force = mg = 2×9.8 = 19.6 N