A random sample of 50 suspension helmets used by motorcycle riders and automobile race-car drivers was subjected to an impact test, and some damage was observed on 18 of these helmets. (a) Find a 95% two-sided confidence interval on the true proportion of helmets, denoted by p, that would show damage from this test and give an interpretation. (b) Using the point estimate of p from the 50 helmets, how many helmets must be tested to be 95% confident that the marginal error E is less than 0.02? (c) How large must the sample be if we wish to be at least 95% confident that the marginal error E is less than 0.02 regardless of the true value of p