Substances A and B have retention times of 16.40 and 17.63 minutes, respectively, on a 30.0 cm column. An unrestrained species passes through the column in 1.30 min. The peak widths at the base for A and B are 1.11 and 1.21 minutes, respectively. Calculate a) column resolution, b) average number of plates in the column, c) plate height.