This is the problem that I am stuck on:

https://www.codecademy.com/courses/python-beginner-P5YtY/1/4?curriculum_id=4f89dab3d788890003000096#

My error message:

Oops, try again. trip_cost('Charlotte', 9) raised an error: unsupported operand type(s) for -: 'str' and 'int'

```
My code:
def plane_ride_cost(city):
if city == "Charlotte":
return 183
elif city == "Tampa":
return 220
elif city == "Pittsburgh":
return 222
elif city == "Los Angeles":
return 475
def rental_car_cost(days):
cost = 40*days
if days >= 7:
return cost-50
elif days >= 3:
return cost-20
return cost
def hotel_cost(days):
return 140*days
def trip_cost(days,city):
sum = rental_car_cost(days) + hotel_cost(days) + plane_ride_cost(city)
print sum
return sum
```