Consider the following recursive algorithm that calculates the gcd of two integers a and b:

procedure gcd$($a$,$ b: nonnegative integers with a $<$ b$)$

if a $=0$ then return b

else return gcd$($b mod a$,$ a$)$

Identify the correct steps involved in finding gcd$(8,13)$ using the given algorithm. $($Check all that apply$)$