Four numbers are chosen at random from {1,2,3............,40}. The probability that they are not consecutive, is

Question

$$\begin {array} {1 1} (a)\;\frac{1}{2470} & \quad (b)\;\frac{4}{7969} \\ (c)\;\frac{2469}{2470} & \quad (d)\;\frac{7965}{7969} \end {array}$$