4/7 Global name "none" not defined


So i'm pretty stumped on 4/7. I keep on getting an error message that says

"An error was raised for rental_car_cost(1): global name 'none' is not defined"

I'm super stumped by this because I'm not defining none in anyway aside from in the else statement. Anybody know why i'm getting this message?

Here is my code for the exercise:

def rental_car_cost(days):
daily = 40 * days
if days >= 7:
daily = days - 50
return daily
elif days >= 3:
daily = days - 20
return daily
return none


This line

return none

should be

return None #This is the builtin keyword