A small company has one color printer and one black-and-white printer, each printing at different rates. The color printer, working for 5 minutes and the black-and-white printer working, working for 3 minutes, print a total of 70 pages. When the black-and-white printer works for 6 minutes and the color printer works for 9 minutes, they print a total of 135 pages. This is modeled by the situation below, where b is the number of pages per minute of the black-and-white printer and c is the number of pages per minute of the color printer 3b + 5c = 70 and 6b + 9c = 135 How many pages per minute does the black-and white printer print?