The values of $a$ and $b$ such that $\mathop {\lim }\limits_{x \to 0} \frac{{x(1 + a\cos x) - b\sin x}}{{{x^3}}} = 1$ are:

  • A
    $a = \frac{5}{2}, b = \frac{3}{2}$
  • B
    $a = \frac{5}{2}, b = -\frac{3}{2}$
  • C
    $a = -\frac{5}{2}, b = -\frac{3}{2}$
  • D
    None of these

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