I need to produce this for class...

Create a button called “GO TO OTHER WEBSITES” on your form that will call a function to give a popup window to go to the user’s choice of url and window size.
The function will use a prompt box to give the user at least 3 choices of urls (other websites related to your website) to choose from.
Use a switch statement to set the chosen url and validate the user choice, do not continue until you have a valid choice.
The user will then be prompted to enter the height and width of the window in pixels. This must be validated for a minimum height and width of 300.
Display the chosen url in a window using this resolution. (Hint: to set the additional properties of the window.open method you will need to create a string variable to set the width and height.)

Not too hard I thought,
I can do a switch statement okay and this is my code and I can have a set window size, setting it up to have a prompt for the user to set width and height and a min value is proofing more difficult

function myPopup2(){
var url = Number (prompt("Which website do you choose? 1. Google 2. Yahoo 3. Moodle", ""));
switch (url) {
case 1:
window.open(url="http://www.google.com/", "myWindow","status = 1, height = 300, width = 300, resizable = 0");

case 2:
window.open(url="https://au.yahoo.com/", "myWindow","status = 1, height = 300, width = 300, resizable = 0");

case 3:
window.open(url ="http://learn.tafesa.edu.au/","myWindow","status = 1, height = 300, width = 300, resizable = 0");


alert("Please enter number 1, 2, or 3 to select a website");