Ok. 50 soda bottles are made in 2 minutes. We need to know how many could be made in 1. Dividing 2 by 2 gives us one minute. So if we divide 50 by 2, keeping the ratio the same, gives us 25. Thus, 25 bottles can be made in 1 minute. Hope that helps!!!
I am old, so I like to use paper & pencil
Parameterize S by the vector function

with 0 ≤ u ≤ π/2 and 0 ≤ v ≤ π/2.
Compute the outward-pointing normal vector to S :

The integral of the field over S is then



-they can get the same answer