A mass of \( 10 \, \text{kg} \) is suspended vertically by a rope of length \( 5 \, \text{m} \) from the roof. A force of \( 30 \, \text{N} \) is applied at the middle point of rope in horizontal direction. The angle made by upper half of the rope with vertical is \( \theta = \tan^{-1}(x \times 10^{-1}) \). The value of \( x \) is ___________.
(Given, \( g = 10 \, \text{m} / \text{s}^2 \) )