Not related to the refund at all, but: Why would you turn off the monitor and not the computer? Even when idling it eats way more power than a monitor in standby.

Seems like something you would think about while, you know, designign a product? And not after its release?

Especially in a middle school math/physics setting, I would expect reasonable units. Otherwise, how would kids understand the relationship between force and acceleration? Do you use mile / hour / min for the acceleration due to gravity as well? Do you have a funky replacement for Newton too?

That’s not the problem. Coming from metric, I expected m s^-2 for acceleration. The imperial units for distances are weird enough in their own right – but using two different units of time for the two time derivatives is truly unholy.

I was not ready for the truly unholy unit of mile per hour per minute

The natural representation would be the transient solution u(t) or i(t). Harmonic solutions are merely a special case, for which it turned out complex numbers were useful (because of the way they can represent rotation). They certainly serve a purpose there, but imo this is not an instance of ‘complex numbers appearing in nature’.

But that is hardly a ‘natural occurence’ of complex numbers - it just turned out that they were useful to represent the special case of harmonic solutions because of their relationship with trig functions.

Julia?