5/7 Pull it Together - Error


#1

When I submit, I get this error - "Oops, try again. trip_cost('Los Angeles', 3) raised an error: cannot concatenate 'str' and 'NoneType' objects"

def hotel_cost(nights):
return 140*nights

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):
cost = days * 40
if days >= 7:
return cost - 50
elif days >= 3:
return cost - 20
elif days < 3:
return cost

def trip_cost(days, city):
return hotel_cost(days) + plane_ride_cost(city) + rental_car_cost(days)


#2

Look at the order of the arguments