Why does the command exp$1()$ give a different answer than exp$2()?$

$($b$)$

Why does the command exp$\_$y$()$ not throw an error? Explain in detail what is happening.

Hint: Does exp$\_$y$()$ output a numeric value? What does it output?

$($c$)$

Without redefining the global objects x or y$,$ changing the definition of the exp$\_$y$()$ function, or creating any

new objects, use the exp$\_$y$()$ function to calculate the fourth power of fifteen.

$9$