A counter is constructed with three D flip-flops. The input-output pairs are named as $\left(D_0, Q_0\right)$, $\left(D_1, Q_1\right)$ and $\left(D_2, Q_2\right)$, where the subscript 0 denotes LSB. The output sequence is desired to be Graycode sequence $000,001,011,010,110,111,101$ and 100 , repeating periodically. Note that the bits are listed in the $Q_2 Q_1 Q_0$ format. The combination logic expression for $D_1$ is

In the given circuit, for voltage V_y to be zero, the value of β should be ______. (Round off to 2 decimal places).

In the given circuit, for maximum power to be delivered to R_L, its value should be ______ Ω. (Round off to 2 decimal places.)

In the circuit, switch 'S' is in the closed position for a very long time. If the switch is opened at time t = 0, then i_L (t) in amperes, for t ≥ 0 is