Consider the following algorithm for computing Fibonacci numbers:

REC$\_$FIBONACCI$($n$)$

if $($n$=0$ or n$=1)$ return $1$

else return REC$\_$FIBONACCI$($n$-2)+$REC$\_$FIBONACCI$($n$-1)$

How many times REC$\_$FIBONACCI calls itself when given n$=4$ as input?

a$.4$

b$.6$

c$.8$