D 12.14 A class B output stage operates from ±10-V supplies. Assuming relatively ideal transistors, what is the output voltage for maximum power-conversion efficiency? What is the output voltage for maximum device dissipation? If each of the output devices is individually rated for 5-W dissipation, and a factor-of-2 safety margin is to be used, what is the smallest value of load resistance that can be tolerated, if operation is always at full output voltage? If operation is allowed at half the full output voltage, what is the smallest load permitted? What is the greatest possible output power available in each case? 10 V; 6.37 V; 2.74, 18.25 W; 3.86, 3.24 W