A single-valued function is an emphatic term for a mathematical function in the usual sense. That is, each element of the function's domain maps to a single, well-defined element of its range.By default, we always consider function as a single valued function except when clearly mentioned that function is a multi-valued function.
So, the number of single valued functions from A to B = number of functions from A to B.
Let an eg.
A ={1,2} ,B={a,b }
1. f(1)=f(2)=a
2.f(1)=f(2)=b
3.f(1)=a and f(2) =b
4.f(1)=b and f(2) =a
The total number of single valued functions from set A to another set B =∣ B ∣^{∣ A ∣ }^{ }= n^{m}
The correct answer is n^{m} .