The paper "Microwave Observations of Daily Antarctic Sea-Ice Edge Expansion and Contribution Rates" (IEEE Geosci. and Remote Sensing Letters, 2006: 54-58) states that "The distribution of the daily sea-ice advance/retreat from each sensor is similar and is approximately double exponential." The proposed double exponential distribution has density function f(x) = .5e for * < x < *. The standard deviation is given as 40.9 km.

a. What is the value of the parameter A?

b. What is the probability that the extent of daily sea-ice change is within 1 standard deviation of the mean value?