Here is a funciton prototype and some possible functions calls: int day$\_$of$\_$week$($int year, int month $=1,$ int day $=1)$; $//$ Possible function calls: cout $<<$ day$\_$of$\_$week$()$; cout $<<$ day$\_$of$\_$week$(1995)$; cout $<<$ day$\_$of$\_$week$(1995,10)$; cout $<<$ day$\_$of$\_$week$(1995,10,4)$; How mant of the function calls are illegal? c$++$