"Ah" = Amp hours? Then you can answer 1) by using the definition of a an Amp. 1 Amp is a "rate of flow" of 1 coulomb per second. You can pretend that 84 Amp hours means (84 Amp)(1 hour) To make progress, you must convert Amps to coulombs per second and convert 1 hr to seconds.
(84 Amp hours could also mean 42 Amps flow in 2 hours, but you would get the same answer if you decrease the Amps and increase the seconds properly.)
You can measure energy in Joules or Watthours or kilowatthours etc.
Let's try Joules.
A Watt is the the unit of power equal to 1 joule of energy per 1 second.
So
1 watt = (1 joule)/ (1 second) and
1 joule = (1 watt)(1 second)
1 Watt is also equal to (1 volt)(1 amp), though this may not be obvious.
So 1 joule = (1 Watt)( 1 second) = (1 volt)(1 amp)/ (1 second)
Replace 1 volt by 12 volts, replace 1 amp by 84 amps and replace 1 second by the number of seconds in an hour to get the number of watts.
