Answer
(a) lees than
(b) $20\%$
Work Step by Step
(a) We know that in the given scenario, the volume of the submerged portion of the block will be less than before when the oil is not poured.
(b) We know that
$\frac{V_2}{V}=\frac{\rho-\rho_{\circ}}{\rho_w-\rho_{\circ}}$
We plug in the known values to obtain:
$\frac{V_2}{V}=\frac{900Kg/m^3-875Kg/m^3}{1000Kg/m^3-875Kg/m^3}=0.20=20\%$
