a 2 kg

let v be vel of ball just before striking, and compression of spring be x

so, ¹/₂mv²+mgx=¹/₂kx²

let the ball fall from height h from rest
thus,v²=2gh

thus, ¹/₂m*2gh=¹/₂kx²-mgx
or, h=^{(1/₂kx2-mgx)}/_(mg)

putting values we get h

karna hi parega!!!!!!!!:P

apparently my soln is correct but it is no where given that pan is massless and n where given collision is elastic.....:P