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Functions
Helper Functions

We can also use the return value of a function inside another function. These functions being called within another function are often referred to as helper functions. Since each function is carrying out a specific task, it makes our code easier to read and debug if necessary.

If we wanted to define a function that converts the temperature from Celsius to Fahrenheit, we could write two functions like:

``````function multiplyByNineFifths(number) {
return number * (9/5);
};

function getFahrenheit(celsius) {
return multiplyByNineFifths(celsius) + 32;
};

getFahrenheit(15); // Returns 59``````

In the example above:

• `getFahrenheit()` is called and `15` is passed as an argument.
• The code block inside of `getFahrenheit()` calls `multiplyByNineFifths()` and passes `15` as an argument.
• `multiplyByNineFifths()` takes the argument of `15` for the `number` parameter.
• The code block inside of `multiplyByNineFifths()` function multiplies `15` by `(9/5)`, which evaluates to `27`.
• `27` is returned back to the function call in `getFahrenheit()`.
• `getFahrenheit()` continues to execute. It adds `32` to `27`, which evaluates to `59`.
• Finally, `59` is returned back to the function call `getFahrenheit(15)`.

We can use functions to section off small bits of logic or tasks, then use them when we need to. Writing helper functions can help take large and difficult tasks and break them into smaller and more manageable tasks.

### Instructions

1.

In the previous exercise, we created a function to find the number of monitors to order for an office. Now let’s write another function that uses the `monitorCount` function to figure out the price.

Below `monitorCount` Create a function declaration named `costOfMonitors` that has two parameters, the first parameter is `rows` and the second parameter is `columns`. Leave the function body empty for now.

2.

Time to add some code to the function body of `costOfMonitors` to calculate the total cost.

Add a `return` statement that returns the value of calling `monitorCount(rows, columns)` multiplied by `200`.

3.

We should save the cost to a variable.

Declare a variable named `totalCost` using the `const` keyword. Assign to `totalCost` the value of calling `costOfMonitors()` with the arguments `5` and `4` respectively.

4.

To check that the function worked properly, log `totalCost` to the console.