Statistics

Let \(\mathrm{a}, \mathrm{b}, \mathrm{c} \in \mathbf{N}\) and \(\mathrm{a}< \mathrm{b}< \mathrm{c}\). Let the mean, the mean deviation about the mean and the variance of the 5 observations \(9,25, a, b, c\) be 18, 4 and \(\frac{136}{5}\), respectively. Then \(2 a+b-c\) is equal to ________