A double pipe heat exchanger is to be designed to cool 5 gallons per minute (gpm) of hot oil from 250°F to 120°F using 10 gpm of cooling water available at 70°F. The heat exchanger is to consist of 12-foot sections of ¾"-16 gauge copper tubing inside a 1 ½"-16 gauge copper tube with water flowing in the annular space. How many sections are required if the flow is: (a) Concurrent; (b) Countercurrent?