Which formula would you use to calculate the number of new subnets?

Group of answer choices

$2$y$,$ where y is the number of zeroes in the subnet mask

$2$y$,$ where y is the number of ones in the network ID extension

$2$y$,$ where y is the number of bytes you add to the subnet mask

$2$y$,$ where y is the number of bits you add to the subnet mask