The ABCD parameters of the following 2-port network are

In the circuit shown, the voltage V_x (in Volts) is ______.

For the circuit shown in the figure, the Thevenin equivalent voltage (in Volts) across terminals a-b is _____.

Let $$\widetilde x\left[ n \right]\, = \,1 + \cos \left[ {{{\pi n} \over 8}} \right]$$ be a periodic signal with period 16. Its DFS coefficients are defined by
$${a_k}$$ = $${1 \over {16}}\sum\limits_{n = 0}^{15} {\widetilde x} \left[ n \right]\exp \left( { - j{\pi \over 8}kn} \right)$$ for all k. The value of the coeffcients $${a_{31}}$$ is _____________________.