The standard deviation of the lifespan of a certain brand of LED light bulbs is 11 months. The quality control department at this company takes a random sample of 85 LED light bulbs and finds the mean lifespan of sample is 140 months. What is the probability that this sample mean is within 4 months of the mean of all light bulbs produced by the company? Round the solution to four decimal places, if necessary. P(a within 4 months of /)