A uniform metal chain of mass m and length L passes over a massless and frictionless pulley. It is released from rest with a part of its length ℓ is hanging on one side and rest of its length L−ℓ is hanging on the other side of the pully. At a certain point of time, when ℓ=xL, the acceleration of the chain is 2g. The value of x is _____.
)
(a) 6
(b) 2
(c) 1.5
(d) 4