GTX 660 Ti Power Supply Question

Hello,
I recently got a GTX 660 Ti and I was wanting to make sure that i put in the right 6 Pin Power Inputs into it so that I don't mess up the card. I have four graphics cards inputs and Im not sure which pair of two would be best to use with the card.

Pair 1:
P3 - 6-pin Graphics Card (+12VE 6A)
P4 - 6-pin Graphics Card (+12VE 6A)

Pair 2:
P15 - 6-pin Graphics Card (+12VB 10A)
P16 - 6-pin Graphics Card (+12VC 10A)

They are both part of a standard 1KW Dell PSU from an XPS720. Which one of the two paris would be better to use?