It does not matter whether we use the R’s or the C’s since when we use impedance in the next section, we will arrive at the same final values.
Some of the transfer functions in Appendix E have a gain constant K. Because ratio of resistors, it will not be affected by frequency shifting resistors associated he K factor do not have to be changed with the other R 's of the circuit, but they ;hanged if it is convenient. We may say that the R’s associated with the K factor frequency dependent.