60i
if you go to mode on your calculator then Chang it from "real" to "a+bi" you can solve for unreal numbers. if you press "2nd" then "." it makes an "i"
The first option is cheaper if that’s what you’re asking.
It’s cheaper because it has a smaller slope so overall will have a lower price than the other option.
Meters cubed. All things that have to do with volume are always cubed.