100ml of 3mM NaCL is mixed with 80 ML of 3.6mM MgCl2 at 293K. Calculate the osmotic pressure of each starting solution and that of the mixture, assuming that the volumes are additive and that both salts dissociate completely into their component ions. So I got .0722 ATM for NACL and .0867 ATM for MgCl2 (not sure if I need to divide those by i). I'm not sure what the equation for adding these two pressures together would be though.