So I already figured out a way to how this code works but in the instructions it tells us to use sum().

"Like the example above, have your function return the sum of calling the rental_car_cost(days), hotel_cost(days), and plane_ride_cost(city) functions."

I don't understand how it wants us to use a sum() if there are three functions it wants us to add. The only way I could see me using sum() is if I define another function and within that function I add two of those three functions together. Then add the new function that I just created with one of the functions I didn't put in the new one.

Ex.

def A

def B

def C

'''def Z:

return sum(A, B, C) this wont work because 3 functions'''

def D

return A + B

def E

return sum(D, C)

```
def hotel_cost(days):
return 140 * days
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):
if days >= 7:
return days * 40 - 50
elif days >= 3 and days < 7:
return days * 40 - 20
else:
return 40 * days
def trip_cost(city, days):
return rental_car_cost(days) + hotel_cost(days) + plane_ride_cost(city)
```