A difficult question from my friend

I have a dwarf (Artisan) character in this game so many friends come to me with a lot of deals. The last task they gave to me was following.

Friend comes to me and says "Hi. I have 300 crystals C grade and i need to create spiritshots, but I don't have adena to buy soul ore. Could you please create some quantity of soulshots and the rest of crystalls leave to yourself as a pay for soul ore?"

I started to think. And my mind did the crytical error... The next day i bought six bottles of beer and get this f**ked formula to do his task and dont trick me and him.

So i get the following universal formula:

Y = (K*KRIS/(K*KRIS + N*RUD)) * X

Where
RUD - The price of the soul/spirit ore
KRIS - The price of the one crystall
K - Number of crystalls in recipe
N - Number of soul/spirit ore in recipe
X - Nuber of crystalls friend gave to me
Y - The result number of crytalls i need to convert into shots and give'em to him
without material losses

The rest of crystalls i will leave in my warehouse :)