Find the second derivative of y equals 6 x cos x. a.) fraction numerator d squared y over denominator d x squared end fraction equals short dash 6 cos x b.) fraction numerator d squared y over denominator d x squared end fraction equals short dash 12 sin x minus 6 x cos x c.) fraction numerator d squared y over denominator d x squared end fraction equals short dash 12 sin x plus 6 x cos x d.) fraction numerator d squared y over denominator d x squared end fraction equals 6 cos x