A battery is charged at a potential of 15 V for 8 hours when the current flowing is 10 A. The battery on discharge supplies a current of 5 A for 15 hours. The mean terminal voltage during discharge is 14 V. The "Watt-hour" efficiency of the battery is [CBSE PMT 2004]

• A.            82.5%                                      
• B.            80 %
• C.            90%                                          
• D.            87.5%