An article in a local newspaper reported that dogs kept as pets tend to be overweight. Veterinarians say that diet and exercise will help these chubby dogs get in shape. The veterinarians propose two different diets (diet A and diet B) and three different exercise programs (Plan1, Plan2 and Plan3). Diet A: owners control the portions of the dog food and dog treats; Diet B: a mixture of fresh vegetables with the dog food and substitute regular dog treats with baby carrots. Plan1 : three 30-minute walks a week; Plan2: 20 minute walks three times a days; Plan 3: 20 minute walks daily. Sixty dog owners volunteer to take part in an experiment to help their chubby dogs lose weights.