In new advertising, the welding union advertises that 80% of its membership has taken a registered welding course. In a sample of thirty welders, eighteen indicated that they had attended a registered welding course. Construct a 95% confidence interval for the proportion of all welders who have attended a registered welding course. Can the union make this claim based on the sample? Use your confidence interval to support your answer. If the union decides to collect more data, how many would we need to sample to be 99% confident of the results with a 0.01 margin of error? Use the estimated proportion from the initial sample to calculate the sample size.