A university financial aid office polled a random sample of 728 undergraduate students and 821 graduate students. Each of the students was asked whether or not they were employed during the previous summer. 441 of the undergraduate students and 401 of the graduate students said that they had worked during the previous summer. Give a 80% confidence interval for the difference between the proportions of undergraduate and graduate students who were employed during the summer. Step 1 of 3: Find the point estimate that should be used in constructing the confidence interval. Round your answer to three decimal places.