Question: A university has 25,000 students, of whom 17,000 are undergraduates. The housing office takes a simple random sample of 500 students; 357 out of the 500 are undergraduates. Fill in the blanks.

(a) For the number of undergraduates in the sample, the observed value is ________________

but the expected value is __________________

(b) For the percentage of undergraduates in the sample, the observed value is ______

but the expected value is _____________