A signal is transmitted digitally over a 4-kHz noiseless channel with one sample every 125 sec. How

A signal is transmitted digitally over a 4-kHz noiseless channel with one sample every 125 µsec. How many bits per second are actually sent for each of these encoding methods?
(a) CCITT 2.048 Mbps standard.
(b) DPCM with a 4-bit relative signal value.
(c) Delta modulation.