A $4 \times 4$ digital image has pixel intensities $(U)$ as shown in the figure. The number of pixels with $U \leq 4$ is:
$$\begin{array}{|l|l|l|l|} \hline 0 & 1 & 0 & 2 \\ \hline 4 & 7 & 3 & 3 \\ \hline 5 & 5 & 4 & 4 \\ \hline 6 & 7 & 3 & 2 \\ \hline \end{array}$$
- $3$
- $8$
- $11$
- $9$
