Ah yes, vocabulary must fit topic. :-) I did wonder about 'power'. Almost said 'force' but that didn't seem quite right either. As for "energy is the capacity for work", I'm thinking. "Capacity" = "the maximum amount that something can contain". Is that the same as "capacity for work"?
Notice how I skip the math? :-)
No it would meaning 5 rather than 2 in this dictionary: https://www.merriam-...ionary/capacity , i.e. capability rather than volume.
As for the fairly trivial arithmetic, this is little more than you need to understand an electricity bill.