HRA Deduction Dilemma: Should We Apply Metro or Non-Metro Rates for an Employee Living in Thane?

Hi all, please help me out. Our company is situated in Mumbai, and we are providing HRA deduction to all employees at 50% of the basic salary as per income tax laws. Since Mumbai is a metro city, one of the employees has produced rent receipts for his stay at a rental house in Thane (which is a non-metro city).

Please let me know whether we should give him a deduction of HRA at 50% of the basic salary (as our company is in a metro city) or whether we should give him a deduction of HRA at 40% of the basic salary (as he is from Thane, a non-metro city).

Please help me, it's urgent.

Can anyone provide me with the list of metro cities in India (ideally from a government document)?