Prompt Help

I need help with a prompt that says:
"Specify the operation you want the machine to perform
a Simple Math calculation
b Simple Physics formulae
c Quote of the Day"

That part I have down but I want it so that when they enter "a" JavaScript uses compute_Math_op(), "b" compute_Physical_quantities, or "c" quote_of_the_day() function.

Thus far I have
<script type="text/javascript">
var y = prompt("Specify the operation you want the machine to
perform /n a Simple Math calculation /n b Simple Physics formulae /n c
Quote of the Day","");
switch(x){

case ‘a’: compute_Math_op();
break;
case ‘b’: compute_Physical_quantities();
break;
case ‘c’: quote_of_the_day();
break;
}
</script>
Really appreciate any help.
Thanks

 

<script type="text/javascript">
var y = prompt("Specify the operation you want the machine to
perform /n a Simple Math calculation /n b Simple Physics formulae /n c
Quote of the Day","");
switch(y){
case ‘a’:
compute_Math_op();
break;
case ‘b’:
compute_Physical_quantities();
break;
case ‘c’:
quote_of_the_day();
break;
}
</script>

Code (markup):

Isn't it suppose to be switch(y)?

 

var y = prompt('Specify the operation you want the machine to perform:'
	+'\n a Simple Math calculation'
	+'\n b Simple Physics formulae'
	+'\n c Quote of the Day', '');
switch(y){
	case 'a':
		compute_Math_op();
		break;
	case 'b':
		compute_Physical_quantities();
		break;
	case 'c':
		quote_of_the_day();
}

PHP: