What is the formula for calculating circular mil?

A$.CM=($ diameter $in$ mils ${)}^2$

B$.CM=K($ diameter $in$ mils ${)}^2$

c$.CM=($diameter in mils$)$

D$.CM=2($ diameter $in$ mils ${)}^2$

If a current of $20$ amps flows through a $55$ feet #$15$ Iron wi wire will drop?

$55..$

find secondary voltage of a transformer with $240$ volts o $40$ amps on the primary, and $20$ amps on the secondary $4020.$What is the formula for calculating circular mil?

A$.CM=($ diameter $in$ mils ${)}^2$

B$.CM=K($ diameter $in$ mils ${)}^2$

c$.CM=($diameter in mils$)$

D$.CM=2($ diameter $in$ mils ${)}^2$

If a current of $20$ amps flows through a $55$ feet #$15$ Iron wi wire will drop?

$55..$

find secondary voltage of a transformer with $240$ volts o $40$ amps on the primary, and $20$ amps on the secondary $4020.$