IF/THEN js help for forms

hello

It's probably super simple but I'm a total novice with acrobat forms.

what I have so far to show the shipping cost is:

var f = this.getField("SubTotal");
event.value = Math.max(7, Math.floor(f.value * 0.1));

so I have a minimum of $7 and for the rest it's 10% of the subtotal
and that works fine

BUT

I need to add a way if it the subtotal is more than $250 that the shipping shows the word "FREE"

I know this is wrong but just to show what I'm trying to get to:

var f = this.getField("SubTotal");
if (SubTotal == >250)
event.value = 'FREE';
else
event.value = Math.max(7, Math.floor(f.value * 0.1));

thank you for your time