Compare the total copper cross sections in terms of current-carrying capacity for a single-phase and a three-phase 120 V system with effective load resistance of 15 Ω.

• single-phase 32 A; three-phase 16 A
• single-phase 16 A; three-phase 8 A
• single-phase 8 A; three-phase 4 A
• single-phase 16 A; three-phase 0 A