Consider a digital music service like Amazon or Apple. What are some of the major cost categories? Are they mostly fixed or mostly variable?

Consider a ride$-$sharing service like Uber or Lyft$.$ What are some of the major cost categories? Are mostly fixed or mostly variable? How are the costs different from those incurred by the drivers?

Pick a unit of a hospital $($like intensive care or maternity$).$ Name one example of a direct materials cost, one example of a direct labor cost, and one example of an indirect cost.

Please provide substantive explanations and support your responses.