Recently, a random sample of 13 - 18 year olds was asked, "How much do you currently have in savings?" The data in the table represent the responses to the survey. Savings (in dollars) 0 - 199 200 - 399 400 - 599 600 - 799 800 - 999 1000 1199 1200 1399 (a) Approximate the sample mean amount of savings. Frequency 337 85 64 17 11 5 2 (b) Approximate the sample standard deviation of savings.