Write a function to multiply all the numbers in a list and divide with the length of the list.
def multiply_num(numbers):  
    total = 1
    for x in numbers:
        total *= x  
    return total/len(numbers) 
<s>[INST]<<SYS>>Given a task and its code, generate test cases for the code.<</SYS>>Write a function to multiply all the numbers in a list and divide with the length of the list.
def multiply_num(numbers):  
    total = 1
    for x in numbers:
        total *= x  
    return total/len(numbers) [/INST]assert multiply_num((8, 2, 3, -1, 7))==-67.2
assert multiply_num((-10,-20,-30))==-2000.0
assert multiply_num((19,15,18))==1710.0</s>