The dean of a college wants to know the average time spent (in hours) by the students of his college in the library.He takes a sample of 225 students visiting the library and calculates the meantime and standard deviation, which comes out to be 6 and 1.5, respectively.Find the interval in which the average time spent in the library by the entire population might lie with a confidence level of 90%.

a). (7.531, 8.110)

b). (5.5, 7.5)

c). (4.83, 7.21)

d). (5.835, 6.165)