State Archimedes’ principle?

State whether upthrust will increase or decrease, if:

(a) the volume of solid increases.

(b) the density of a liquid in which the solid floats decrease.

A ball weighing $4 \mathrm{kg}$ of density $4000 \mathrm{kg} {\mathrm{m}}^{-3}$ is completely immersed in water of density ${10}^{3 }\mathrm{kg}/{\mathrm{m}}^3$. Find the force of buoyancy on it.(Given, $g=10 \mathrm{m} {\mathrm{s}}^{-2}$).