Monitoring impedance to leg movements. In an experiment designed to monitor impedance to leg movement, Korean engineers attached electrodes to the ankles and knees of volunteers. Of interest were the voltage readings between pairs of electrodes (IEICE Transactions on Information & Systems, Jan. 2005). These readings were used to determine the signal-to-noise ratio (SNR) of impedance changes such as knee flexes and hip extensions.

a. Six voltage electrodes were attached to key parts of the ankle. How many electrode pairs on the ankle are possible?

b. Ten voltage electrodes were attached to key parts of the knee. How many electrode pairs on the knee are possible?

c. Determine the number of possible electrode pairs such that one electrode is attached to the knee and one is attached to the ankle.