Please hurry i have competitive exam in this month

the change in vol = vol of the rock..(Archi. principle)

length of the tank=60

breadth=50

height or depth=30

orig vol of water=60*50*30

the raised volume=60*50*(30+42)

so rise in vol=[60*50*(72)]-[60*50*30]=60*50*[72-30]=60*50*42

so this is thevol of the rock.