Which limit order will be filled first?

I’m trying to understand which of the following limit orders would be filled first.

Let’s say for argument’s sake stock X is $11.00, person A makes a limit buy for 1 stock X at $10.00 at 10:00am market open and it hasn’t been matched. At 3:30pm person B makes a limit buy for 1 stock X at $10.00 and its not matched. At 3:31pm the market price of stock X hits $10.00. And someone makes a market sell of 1 stock X.

Whose order is filled first? Person A or Person B? Would the filling criteria differ from exchange to exchange or do all exchange operate on the same matching rules.