Two rigs are available for drilling a well in southern California. One rig costs $800/hr but can only pull doubles. The other rigs costs $1,000/hr but can pull thribbles. In this area K is 200 ft/hr and 2,303a, is 0.0004. The time required to pull one stand is about 4 minutes for both rigs. Considering only the cost of the tripping operations, which rig would be best for a well drilled to 7,000 ft? Assume an average bit life of 10 hours for all bits and casing setting depths of 500 and 2,000 ft. Answer: Thribble rig ($151,200 vs. $181,400).