$($A$)$ Show how the J$-$K flip$-$flop can be operated as a toggle FF$.$ Apply a $10-KHz$ square wave to its inputs, and determine its output waveform.

$($B$)$ Connect the Q output of the FF to the CLK input of a second J$-$K flip$-$flop that also has $J=K=1.$ Determine the frequency of the waveform at the second FF output.