The logarithmic mean temperature difference (LMTD) of the condenser is

Question

In a condenser of a power plant, the steam condenses at a temperature of 60⁰C. the cooling water enters at 30⁰C and leaves at 45⁰C. The logarithmic mean temperature difference (LMTD) of the condenser is                       

      (a) 16.2⁰C                                                           (b) 21.6⁰C

      (c) 30⁰C                                                              (d) 37.5⁰C