f i have an 8 ohms(mono) cabinet and a 16 ohms(mono) cabinet what would i set the head to?....

i know 16 and 16 is 8 and 8 and 8 is 4 but im not sure on the mixing

if someone could post what i do for combinations like 16 and 8 and 8 and 4 or 16 and 4 or 4 and 16....

or can it just not work at all?

-thanks