I have a friend with an unknown speaker cab (4x12" speakers) the impedance is 8 ohms across the cab. I think two speakers in series are wired in parallel. Which would make sense thay they are 8ohm speakers.

Two questions What I'm wondering is there anyway to work out the wattage rating of a speaker or the whole cab?

If I am able to find out the wattage rating of one speaker what is the math involved in calculating what the whole cab would be.