The article "Leachate from Land Disposal Residential Construction Waste" (authored by W.J. Weber, Y.-C Jang, T.G. Townsend, and S. Laux, Journal of Environmental Engineering, 128(3): 237 - 245, 2002) presents a study on contamination at landfills containing construction and demolition wastes. Specimens of leachate were taken from a test site. Out of 42 specimens, 26 contained detectable levels of lead. 41 contained detectable levels of arsenic, and 32 contained detectable levels of chromium.
(a) Determine a 90% confidence interval for the probability that a specimen will contain a detectable level of lead.
(b) Determine a 95% confidence interval for the probability that a specimen will contain a detectable level of arsenic.
(c) Determine a 99% confidence interval for the probability that a specimen will contain a detectable level of chromium.