In a double pipe heat exchanger if the inner diameter of inner pipe is 6cms, and outer diameter is 8 cms. respectively and pipe has a length of one metre .If the rate of heat transferred is 60 W. overall heat transfer coefficient based on out side diameter is if temperature differene is 60C Select one:

a. 1.56 W/mC

b. 0.000156 W/m*C

c.0.00156 W/m*C

d. 0.0156W/m*C