An article suggests the lognormal distribution as a model for so2 concentration above a certain forest. suppose the parameter values are μ = 1.8 and σ = 0.9. (a) what are the mean value and standard deviation of concentration? (round your answers to three decimal places.) mean standard deviation (b) what is the probability that concentration is at most 10? between 5 and 10? (round your answers to four decimal places.) at most 10 between 5 and 10