hartke vx410 ohms

hi all - i just picked up a hartke vx410 cab. there are 4 8 ohms 10s and an 8 ohm comp driver. how do they get a total of 8 ohms out of those? if it was just the 4 10s, i could see that with 2 parrallel sets of 2 speakers in series, but where does the comp driver fiqure in?

i also noticed that the 10s are 75 watt each, and the comp driver is 50... where's the 400 watts?

thanks for any info