In Exercises 21-24, use these results from the "1-Panel-THC" test for marijuana use, which is provided by the company Drug Test Success: Among 143 subjects with positive test results, there are 24 false positive (incorrect) results; among 157 negative results, there are 3 false negative (incorrect) results. (Hint: Construct a table similar to Table 4-1 on page 159.) 21. Testing for Marijuana Use a. How many subjects are included in the study? b. How many of the subjects had a true negative result? c. What is the probability that a randomly selected subject had a true negative result?