I have a 6515 Work Centre Printer. It quit printing and said that Yellow toner was out. I thought it was the Yellow drum cartridge. I replaced the drum and then discovered that there are also a whole other set of cartidges. How do I get the printer to use the drums instead of the cartridges? The drums print 48,000 pages. The cartridges print about 6,00 I think. Why are there 2 sets and does the printer use both? I hope someone can help me. Thank you in advance for any help or information.