How will the lists change after calling the functions?

Determine which output will appear in the console after executing the following code. Functions work with lists differently.

def modify_first(lst):
    lst[0] = 123

def reassign(lst):
    lst = [4, 5, 6]

list_a = [1, 2, 3]
list_b = [1, 2, 3]
modify_first(list_a)
print(list_a)
reassign(list_b)
print(list_b)