Setting resolutions for iPad and iPhone

Hello

I have trouble setting resolution when building for iphone and ipad.

I'd like to set 320p for all iphone devices (retina, non-retina) and 720p for all ipads (retina, non-retina)

So for target resolution there are 2 options, Auto (Best Performance) and Auto (Best Quality), when im setting Auto (Best Performance) and building for iphone 4 the resolution is 320p and its ok. but when im running same app for ipad 3 resolution goes to 2048x1536 ?

how can i set manually resolution for each type of device?

Thanks