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# If $5 \cos x +12 \cos y=13$, then the maximum value of $5 \sin x +12 \sin y$ is :

$\begin {array} {1 1} (a)\;12 & \quad (b)\;\sqrt {120} \\ (c)\;\sqrt {20} & \quad (d)\;13 \end {array}$

(b) $\sqrt {120}$