Let $\Sigma=\{a, b, c, d\}$ and let $L=\left\{a^i b^j c^k d^l \mid i, j, k, l \geq 0\right\}$.

Which of the following constraints ensure(s) that the language $L$ is context-free?

The determinant of a $4 \times 4$ matrix $A$ is 3 . The value of the determinant of $2 A$ is

$\_\_\_\_$ . (answer in integer)

Expedite, Hasten, Hurry, $\_\_\_\_$ .

Fill the blank by choosing a word with a meaning similar to that of the words given above.

A black square PQRS has been cut into two parts. One part of it is shown in Panel I. Which one of the shapes in Panel II is the other part?