In our ongoing "Ask CBS News" segment, we've answered your questions about the Gulf oil spill. The response from viewers on Twitter and Facebook has been terrific. Viewers can leave questions on Evening News anchor Katie Couric's Twitter page.
Tonight we answer more of your questions.
A viewer asks: "How effective is burning the oil on the water? Can't they burn the oil before it reaches shore?"
CBS News correspondent Mark Strassman answers: At first these controlled burns were experiments but they've worked. The Coast Guard says they've now burned almost 4 million gallons. Under today's revised leak estimates, that's less than three days of this disaster. And you can't burn it all because first you have to corral the oil. Then you have to wait for calm seas, and the smell from the smoke is toxic. So they also have to wait until they can burn the oil far from shores.
Question: "Why is BP the only company working to clean up the mess? Why don't other companies that have equipment help?"
CBS News correspondent Kelly Cobiella answers: Other companies are helping you just don't see their names across boats or anything like that. They all pay into this Co-op of sorts called the MSRC, the Marine Spill Response Corporation. They actually provide the vessels and equipment once a spill happens and we saw two of their boats out on Pensacola Bay today.
More "Ask CBS News" Oil Spill Questions and Answers: