Hello! This is definitely a tricky question.

Recall that for a floating object, the mass of water displaced = mass of brick+styrofoam (in this case mass of styrofoam is 0). So m_water = m_brick. Also recall that density, rho=m/v or m = rho x v. if m_water = m_brick then rho_water x v_water = rho_brick x v_brick. we know that rho_brick/rho_water = 1.4. If we rearrage our previous formula, rho_brick/rho_water= v_water/v_brick = 1.4. We also know that the volume of water dispaced = 1/2 styrofoam volume, so v_water = 1/2 v_styro.

so: v_water = 1/2v_styro = 1.4v_brick. (1.4~3/2) —> to rearrange this: v_styro ~ (3/2)*(2)v_brick ~ 3v_brick giving you the answer C.