Sam's is interested in two goods, X and Y. His indirect utility function is

U* = M p_x^-0.7 p_y^0.7-1. ( same as U* = M /(p_x^0.7 p_y^1-0.7) )

where M is Sam's income, and p_x and p_y denote respectively the price of good X and the price of good Y.

Sam's market demand function for good X is X*=0.7M/p_x .

Find the compensating variation for Sam given the price of good X rises from 1 to 8 dollars due to a per-unit tax imposed by the government, assuming his income is M=533 and price of good Y is equal to 4.