for a digital time division multiplexing system each voice channel has a bit rate of $64kbps\mathrm{.}32$ voice channels are multiplexed $.$ each channel is encoded using $10$bitpcmcode. the system uses a single bit for timing at the end of each frame. the bit interval is :

Select one:

a$.0\mathrm{.}647$ micro second

b$.0\mathrm{.}389$ micro second

c$.12\mathrm{.}5$ micro second

d$.125$ micro second