2011SP-II-42

Ans: B
Consider the function $y=a\cos (x^{\circ }+b)$.

$a$ represents the enlargement along the $y$-axis. That is the graph is enlarged by $a$ times along the $y$-axis.

The sign of $a$ represents the reflection about the $x$-axis. If the sign of $a$ is negative, the graph is reflected about the $x$-axis.

$b$ represents the translation along the $x$-axis. If $b$ is positive, the graph translates to the left $b$ units. If $b$ is negative, the graph translates to the right $-b$ units.

Note that the graph is reflected about the $x$-axis, enlarged $3$ times along the $y$-axis and translates to the left $40$ units.

Hence, $a=-3$ and $b={40}^{\circ }$.