Read the passage, "Computers vs. Books" by ReadWorks. Read the following sentences: "Mrs. Murphy started to list off things she didn't have as a child, like an mp3 player and a flat screen television. 'Also, since I had many brothers and sisters, we had to pitch in more. I helped my mom cook dinner, and we repaired our clothes ourselves when they tore, ' she said, tapping Mia on the nose." As used in the passage, what does the phrase "pitch in" mean?