Examine the value-added versus non-value-added times for some other services. For example:
(a) Handing in an assignment for marking if you are currently studying for a qualification (what is the typical elapsed time between handing in the assignment and receiving it back with comments?). How much of this elapsed time do you think is value-added time?
(b) Posting a letter (the elapsed time is between posting the letter in the box and it being delivered to the recipient).
(c) Taking a garment to be professionally dry cleaned.