Sr Acquisition Analyst

When it is in the best interest of the government to exercise a priced FAR 52.217-8 extension instead of exercising the last one-year priced Option, what pricing should be used?  Would it be the six-months of the last one-year priced Option on contract, or the priced FAR 52.217-8 Option, which includes the cost escalation of the un-exercised Option?  What would be the appropriate authority?