A metal block of volume 500cm3 weighs 50 N in air. It is hung from a spring balance and completely immersed in water. A second light string attached to its bottom is fixed to the floor of the tank so that the block remains fully submerged. The spring balance shows 55 N. Taking g=10m/s2 and density of water =1000kg/m3, determine the tension in the lower string.
(a) 15N
(b) 10N
(c) 5N
(d) 0N