Find the running time equation of this Python Function

def foo(L): # L is a list with n numbers

if L == []:

return 5

s = 0

for x in L:

s = s+x

A = L[0:len(L)//2]

B = L[len(L)//4 : len(L)//2]

C = L[len(L)//2 : 3*len(L)//4]

return foo(A) + foo(B) + foo(C) + S