Consider a CSMA$/$CD network that transmits data at a rate of $100Mbps$ over a $xkm$ cable with the signal speed of $20000k\frac{m}{s}.$ If the minimum frame size required for this network is $1250$ bytes, calculate the value of $x$

a$.0\mathrm{.}5km$

b$.2km$

c$.5km$

d$.$ None of the above