The RDW index is expressed by which of the following equation?
(a) [(20th – 80th) Percentile Volume / (20th + 80th) Percentile Volume] X 100 X K
(b) [(20th + 80th) Percentile Volume / (20th – 80th) Percentile Volume] X 100 X K
(c) [(20th – 80th) Percentile Volume / (20th – 80th) Percentile Volume] X 100 X K
(d) [(20th + 80th) Percentile Volume / (20th + 80th) Percentile Volume] X 100 X K