A sample of student enrollment per course at a college is as follows: 12 15 20 22 15 27 21 18 19 18 33 16 18 17 23 28 13 33 32 31 13 32 16 26 25 14 31 29 11 22 (a) Are these data cross-sectional or time series? Why? (b) Group the data, starting with the smallest observation in the data. Clearly show your data grouping steps and manual calculations. (c) Summarize your grouped data in frequency and relative frequency distributions in 2 decimal points. Clearly show your steps and manual calculations. (d) Interpret the second row of your summarized data