16. The difference in volumes of two cubes is 152 m3 and the difference in their one face areas is 20 m2. If the sum of their edges is 10 m, the product of their edges is :

17. If the length of diagonal of a cube is 8 cm. then its surface area is :

18. The area of the base of a rectangular tank is 6500 sq. cm. and the volume of water contained in it 2.6 cubic metres. The depth of water is :