Jolly Blue Giant Health Insurance (JBGHI) is concernedabout rising lab test cost

Jolly Blue Giant Health Insurance (JBGHI) is concernedabout rising lab test costs and would like to know what proportionof the positive lab tests for prostate cancer are actually provencorrect through subsequent biopsy. JBGHI demands a sample largeenough to ensure an error of 2% with 90% confidence. What is thenecessary sample size?