You don't even have to calculate since area doubles every 3 steps.
4 wires = 4 x area = 6 steps. 24-6=18.
4 wires = 4 x area = 6 steps. 24-6=18.
Speaker wire gauge
Do any members know what the "equivalent gauge" would be when you bundle 4 strands of 24 gauge wire together? Thanks!