Great! Now that you’ve got your 3 main costs figured out, let’s put them together in order to find the total cost of your trip.

def double(n): return 2 * n def triple(p): return 3 * p def add(a, b): return double(a) + triple(b)

We define two simple functions,

`double(n)`

and`triple(p)`

that return 2 times or 3 times their input. Notice that they have`n`

and`p`

as their*arguments*We define a third function,

`add(a, b)`

that returns the sum of the previous two functions when called with`a`

and`b`

, respectively. Notice that even though the names of the parameters for`add(a, b)`

are different than the names of the parameters for`double(n)`

and`triple(p)`

we can still pass them into those functions as arguments

### Instructions

**1.**

Below your existing code, define a function called `trip_cost`

that takes two parameters, `city`

and `days`

and returns the *sum* of calling the `rental_car_cost(days)`

, `hotel_cost(days - 1)`

, and `plane_ride_cost(city)`

functions.

Notice that we changed the argument of `hotel_costs()`

from `nights`

to `days - 1`

. Since we want `trip-cost`

to only depend on two parameters, we have to convert the variable `nights`

into `days`

. If you are going to be staying somewhere, the number of nights you stay there is one less than the number of days you were there (imagine a weekend trip to visit family, you leave Saturday and return Sunday, so you visit for two days, but only stay for one night).