A total of 280 observations of Bob Ramos, an assembly-line worker, were made over a 40-hour work week. The sample also showed that Bob was busy working (assembling the parts) during 250 observations. (Round all intermediate calculations to at least two decimal places before proceeding with further calculations.) a) The percent of time Bob is working- 89.29 % (enter your response as a percentage rounded to two decimal placed) b) The number of observations that need to be taken of Bob to be 95% confident with 4% acceptable error (round your response to the immediate higher whole number)