Probability

Five numbers \({x_1},{x_2},{x_3},{x_4},{x_5}\) are randomly selected from the numbers 1, 2, 3, ......., 18 and are arranged in the increasing order \(({x_1} < {x_2} < {x_3} < {x_4} < {x_5})\). The probability that \({x_2} = 7\) and \({x_4} = 11\) is :