Solution:
We have, A={1,2,3,4,5,6}
f(m)+f(n)=7 of m+n=7
Order of (m,n) is {(1,6),(2,5),(3,4),(4,3),(5,2), (6,1)}
f(1)+f(6)=7,f(2)+f(3)=7,f(3)+f(4) =7
f(1)+f(6)=7 has 36×2=72 functions
Similar for f(2)+f(5)=7 and f(3)+f(4)=72
Total number of functions =72+72+72=216
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