Dks drop rates?

What are the average drop rates for Rex dropping a berserker ring, warrrior ring or a dragon hachet? Also witch is better duo briding them or solo maging rex (cash p/hr wise) if I were to solo how much avg would I make an hr I got 99mage 92hp 95prayer and 78 def I would be using a poly staff, glory, torag plate and legs, mystic boot, barrows gloves, spirit shield and a farseer helm.