In an English class, the instructor knows that the number of pages in the final submission of an essay follows an unknown distribution, with a mean of 8 pages and a standard deviation of 4 pages. Suppose that a sample of 71 tests is taken. What is the probability that the total number of pages written in this sample is less than 540.7? Select one:
a. We cannot answer this question with the information given.
b. 0.8100
c. 0.2090
d. 0.7910
e. 1.0000