If Young's modules of elasticity is $\mathrm{Y}=\frac{2\mathrm{mg}{l}^{\mathrm{x}}}{5b{t}^3\mathrm{e}}$.where 'g' is the acceleration due to gravity, 'm' is the mass, ' l ' is the length, ' b ' is the breadth, 't ' is the thickness and 'e' is the elongation, then the value of x is