?? pullup time and pulldown time

sevid

hi,everyone

how to make ur pullup time and pulldown time equal in ur gate, for example, a 4-input NAND gate.

if the efficient resistance of a NMOS in the pulldown network is Rn, the total resistance is 4Rn.

but what's the total resistance or average total resistance of the pullup network, if one PMOS efficient resistance is Rp.

probability is used here?

thanks

sevid