Properties of value x have mortgage value x/2 and unmortgage value 11x/20, for 27 of the properties this is an exact dollar value but Park Place is special.
Cost M$350, Mortgage M$175, unmortgage M$192.5. Half dollars don't exist and would never be useful EXCEPT in this case.
Is there an official ruling for the unmortgage cost of Park Lane? I've always played it as $193 but an argument came up when an opponent only had M$592 and wanted to put houses on Mayfair and Park Lane and unmortgage Park lane on the same turn, it made a difference of M$105 rent the next turn.