Problem

Given:

A household has Cobb-Douglas preferences with U=X^0.4*Y^0.6
Its demands for X and Y are: X = 0.4*M/Px and Y = 0.6*M/Py
Its expenditure function is: M=U*(Px/0.4)^0.4*(Py/0.6)^0.6
Initially, Px=2, Py=2 and M=1000
The government wishes to decrease X to 100 by raising Px appropriately

Determine:

The compensating variation for the policy.