Screen Lock A survey of U.S. adults found that 28% of those who own smartphones do not use a screen lock or other security features to access their phone. You randomly select 150 U.S. adults who own smartphones. Find the probability that the number who do not use a screen lock or other security features to access their phone is (a) at most 40, (b) more than 50, and (c) between 20 and 30, inclusive.