Mass of copper in air = 264 gm

Mass of copper in water = 221 gm

Apparent loss of mass in water = 264 – 221 = 43 gm

∴ Mass of water displaced by copper piece when completely immersed in water is equal to 43 gm.

Volume of water displaced = (mass of water displaced/density of water)

= 43/1.0 = 43.0 cc

∴ Volume of copper piece including volume of cavity = 43.0 cc

Volume of copper block only = mass/density = 264/8.8 =30.0 cc

Volume of cavity = 43.0 – 30.0 = 13.0 cc.