Computing Buttons To Work And Alert Messages?

so here is my "Project" for this class

[URL]

and here are the directions where im stuck at, just right click view source to see the code. I believe what i am doing wrong is where i enter my variables and i dont know how to get an alert message to pop up using an if statement as well as getting the values for the distances to show up correctly

directions:

8. Now we will write some JavaScript to validate the input. We don’t want the user to be able to enter the same origin and destination city when they book a ticket. So we will use an if statement to check that. If they have entered the same origin and destination city then we will tell them that by using an alert statement and make them select again. All of your code to validate the input code goes in between the single quotes of the onClick event in the Calculate Fare button. Follow these steps: a) Assign the value of the origin city to a variable called origin Note that the value that gets assigned to origin is actually 0, 60, 90, 120 or 150 (and NOT Bellingham, Everett, Seattle etc.) since the value we gave to the each element of the list was its distance from Bellingham. This will make our lives easier later when we compute the fare. b) Assign the value of the destination city to a variable called destination in a similar fashion. c) Write an if statement that will test whether origin is equal to destination and if it is then do two things. i. Issue an alert message that says input different origin and destination cities ii. Stop the execution of the JavaScript code in the onClick event. Use return; as the second statement inside the if statement. Remember to use curly braces to denote that two statements are contained within the if statement. Your if statement will have the following structure to it.

if (<put the test you want to do here>)
{
alert(<put the message here>);
return;