could you help me with this question please

4. Students in a survey design course were given an assignment to estimate the average time per week devoted to study in the library by the students registered at a university. The university offers programs at the undergraduate, master's degree and doctoral levels. The number of students registered for the three programs in the university is 1335, 540, and 400 respectively. Since the time spent studying in the library is likely to differ considerably with the program level, the investigators divided the population of students into 3 strata: undergraduate program (stratum 1), master's program (stratum II), and doctoral program (stratum III). A simple random sample of sizes 20, 8 and 6 was selected from strata I, II, and Ill respectively, so that, the total sample is of size 34. The information about weekly time devoted in library is given in the table below. a. Estimate the overall average time spent in library study by students at the university. b. What is the 95% confidence interval of the estimate obtained in a.? Stratum I Stratum II Stratum III 12 10 24 10 14 15 20 14 WONUW 10 Stratum Mean 3.8 9.875 16.167 Stratum Variance 7.958 4.125 24.967