|A| = m and |B| = n , then
No. of functions from A to B = n^m
So total no of functions =4^4
but we have condition x=y so
then total no of functions =4 F= {(0,0),(1,1),(2,2),(3,3)}
Total no of relation on given function F=2^n
Total no of relation on given function F=2^4=16