The article "Reliability of DomesticWaste Biofilm Reactors" (J. of Envir. Engr., 1995: 785-790) suggests that substrate concentration (mg/cm3) of influent to a reactor is normally distributed with µ = .30 and σ = .06.
a. What is the probability that the concentration exceeds .50?
b. What is the probability that the concentration is at most .20?
c. How would you characterize the largest 5% of all concentration values?