Hi. What am I doing wrong?

```
def rental_car_cost(days):
cost=days*40
if days >= 7:
cost =-50
elif days >=3 and days < 7:
cost =-20
else:
return cost
```

My error is:

It looks like rental_car_cost returns None instead of the correct amount (100) for 3 days.

Thanks in advance!!