The \( \text{pH} \) of a \( 0.01 \,\text{M} \) weak acid \( \mathrm{HX} \) \( (K_a = 4 \times 10^{-10}) \) is found to be \( 5 \). Now the acid solution is diluted with excess of water so that the \( \text{pH} \) of the solution changes to \( 6 \). The new concentration of the diluted weak acid is given as \( x \times 10^{-4} \,\text{M} \). The value of \( x \) is ________ (nearest integer)
