Consider the Following Definition of the Recursive Function Mystery $\quad$ Return 0;
Else If (First == Last)

Multiple Choice

Consider the following definition of the recursive function mystery. int mystery(int first,int last)
{
if (first > last)
$\quad$ Return 0;
else if (first == last)
$\quad$ Return first;
else
$\quad$ return first + mystery(first + 1,last - 1) ;
}
What is the output of the following statement?
cout << mystery(6,10) << endl;

A) 13
B) 21
C) 40
D) 42