English

The first couple times it's a bit daunting, but after doing Water Carrier so many times, I've memorized the recipes for Grade 1 and 2 to where it's almost reflex.

And that's the trick; trying different recipes to get 100%. See, there's 5 questions each with 7 answers for a total or 7^5 possibilities (or "recipes") and only 1 of those 16,807 (that's what 7^5 equals) is a 100% recipe that will get you 18 products for maximum profit from NH. It's kind of a puzzle.

To put it in real-world terms, think of it as going to McDonalds for a burger. You don't want to be that person that gets to the head and then sits there for 20 minutes studying the menu, do you? Basically, you're supposed to know the recipe you want to try well enough to just hand them your stuff, answer bapbapbapbapbap, and collect your product about as fast as you'd give your order at McD's because that occupation master wants to go from "Can I take your order?" to "Have a nice day!" just as fast as that McDonalds cashier. Does that explain the short time limit?

But how to know what recipe you want to use before you begin the mission? The game remembers your best recipe for each grade of each occupation, so you don't have to fill up notebooks or brain cells remembering yourself; when you hit P and call up your stats, there's 4 tabs in that window and one of them is Occupations.

If you tried to figure out the recipe yourself without resorting to looking it up, how long it would take would depend on how good your puzzle-solving skills are. If you know the numbers the way many computer/math geeks do, you could use a little logical deduction to develop the technique to narrow it down considerably. While 1-in-16,807 may seem like needle-in-a-haystack, it's really only 1-in-35 ;)

If you want to look it up online instead of trying to solve the puzzle, you should consider doing that before you start the "practice Grade X" mission.