1.The mother of a teenager has heard a claim that 25% of teenagers who drive and use a cell phone reported texting while driving.She thinks that this rate is too high and wants to test the hypothesis that fewer than 25% of these drivers have texted while driving. She polls 40 randomly selected teenagers and 5 of them report having texted while driving.Use a 0.05 significance level to test the mother's claim.

Which formula do I use to find the test statistic?