Write the recursive Running time equation

What is the number of subproblems in the recursive equation?

What is the size of each subproblem in the recursive equation $?$

What is the base case of this program? What is the running time of base case?

Program $2$:

$//$ comment: $A=[a_1,a_2,$dots,$a_n]$ is an input array of size $n0$ with positive

integers $a_1,a_2,$dots,$a_n$

Function Sum$\_$array$($array $\{$:$A=[a_1,a_2,$dots,$a_n])$ :

if array $A$ is empty:

Return $0$

Else $($array A has at least $1$ number in it$)$:

$//$ comment: the recursive call

Return $a_n+$ Sum$\_$array $([a_1,a_2,$dots,$a_{n-1}])$