In the digital-to-Analog converter circuit shown in the figure below,
$${V_{R\,}}\, = \,10V$$ and $$R\, = \,10k\Omega $$

The voltage V₀ is

For the circuit shown, the counter state (Q₁ Q₀) follows the sequence

In the following circuit, X is given by

The Boolean function Y=AB+CD is to be realized using only 2-input NAND gates. The minimum number of gates required is