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7. After several months of close observation an office clerk has found that 27% of the ball-pens that have been used by her office do not write clearly (i.e., ink doesn't flow properly). A 95% confidence interval of the percentage of such defective pens have been found to be (24.5%, 29.5%). How many ball-pens did the clerk observe? (a 1212 (b) 1065 (c) 854 (d) 30 (e) None of the above