A 20 V battery is connected with a parallel combination of resistance 6 Ω and variable R and this combination is connected with 3 Ω resistor. Now the value of the resistance R in the circuit is varied in such a way that the power dissipated in the 3 Ω resistor is maximum. Under this condition the value of R will be

• A. 3 Ω
• B. 9 Ω
• C. 12 Ω
• D. 0 Ω