17% of 19,700 = 3349. So if you add 3349 to 19,700 you get 23,049. So it sounds like it's around a 16-17% markup.
It should be 75 if you divide the area by the amount of sides. I don’t know if I’m right if I’m wrong I’m sorry!
There are 4 quarts in each gallon.
It would take 2 fills of the canteen to make one gallon.
2x5=
10
Also, this image may be helpful.