Resize persistence partition

Currently I'm messing around with using a custom image of Kali. Since the original live was setup on a 16gb flash drive it has a persistence partition setup for the remaining 12gb left over. I've moved alot of stuff over to a 32gb flash and wish to merge the existing persistence partition with the new extra space.

http://i1293.photobucket.com/albums/...psa399bce1.png

Can anyone tell me how to safely merge the existing persistent partition with the new partition, or at least how to resize the sdb2 partition to include sdb3's space as well?
Thank you.