Fluoride emissions (in ppm) from a chemical plant are monitored routinely. The following are 15 observations based on air samples taken randomly during one month of production: 7, 3, 4, 2, 5, 6, 9, 8, 7, 3, 4, 4, 3, 2, 6. Can you claim that the median fluoride impurity level is less than 6 ppm? State and test the appropriate hypotheses using the sign test with a = 0.05. What is the P-value for this test?