buy 3 get 4

What is the best way to set up a buy 3 get 4 type promotion?

I am selling hika serial numbers and we want to sell

1 for $50
or
buy 3 for $150 and get 4

What is the best way to set this up in hikashop?
www.charitymobi.org/index.php?option=com...yout=show&Itemid=183


Thanks! -- Steven

Hi Steven,
I think that the best way to do that will be to use a coupon which will apply a 33.33% (or $50 for example) reduction.
To automatically apply this coupon through the checkout process, you'll have to set the "Auto load in cart if possible" option to YES so that you customers won't have to enter any coupon code through the checkout process.