I have a customer who wants me to first dethatch his yard, then spread gypsum, and finally reseed with 50lbs seed. He already has the seed and 200lbs of gypsum the lot size is about 16000 s.f. He also wants to know if I can get more gypsum, but I have never spread this before, and don't know where to get it. How would you price this? Please Help!