A 75°C Thermoplastic Insulated Type THWN Copper Conductor Can Withstand

A 75°C thermoplastic insulated Type THWN copper conductor can withstand 4200 amperes for one cycle. What is the I ² t let-through value for a noncurrent-limiting circuit breaker that takes one cycle to open? The available fault current is 40,000 amperes.

A) 3,200,000 ampere squared seconds
B) 6,400,000 ampere squared seconds
C) 12,800,000 ampere squared seconds
D) 25,600,000 ampere squared seconds