In school, we are making filters to clean a polluted water. The water is filled with all type of pollution, dirt, bubbles and more. We already made a filter, now we trying to make a new filter or improve our next filter. I think the next filter will make the polluted water cleaner, and remove all the particles, and might be healthy to drink. I hope the next filter will be even better than the last one. When we try the next the filter might be bigger improvement. We have a scoring system the lowest score is the best. My first filter was $3.75 as a score that would be a 1. my group used 1/2 a cup of sand and gravel, 4 cotton balls, and a coffee filter and it was only $3.75. How do you think I can improve my filter?