If you want to know how to locate all rats and conserve time here is a tip, You should first check the rooms that are closest to the book room(dont go inside just hear for a rat). Next you are gonna go to 3 spawn locations(it can be any) to hear(NOT SEE) rats, if u find one take it and find a safe zone if you hear Rin. Coz what i usually do is i check the ones near the book room the ones on the right, If i dont see any there i will check the rats on the left but dont go into the rooms just hear the rat lol. And Also If you are in a safe room (this wont work on the double room or the well room) and the monster goes past left or right go the opposite way, becoz the map isnt that big and you will always end up in the room you want to but make sure to hear her becoz she can somtimes retract