Force of Buoyancy $=\rho V g=1000 \times 10^{-3} \times 10=10\, N$
There will be a reaction force to the buoyant force, by the stone on the water.
Therefore, net force on spring balance is sum of force of buoyancy and weight
of water and beaker $= F _{ B }+ mg =10+1.5 g =10+15=25 \,N$
Net reading of spring balance $=2.5 \,kg$



