If service is fed with service entrance conductors of 500 MCM THHN copper and fused at 400 amps What would be the minimum size of a copper grounding electrode conductor?

For a service rated at 400 amps using 500 MCM THHN copper conductors, the minimum size for a copper grounding electrode conductor (GEC) can be determined using the National Electrical Code (NEC) guidelines. According to NEC Table 250.66, for a service of 400 amps, the minimum size for a copper GEC is 4 AWG. However, if the GEC is connected to a ground rod, it must be a minimum of 6 AWG copper.