A charge of \( 4.0 \, \mu \text{C} \) is moving with a velocity of \( 4.0 \times 10^6 \, \text{ms}^{-1} \) along the positive y-axis under a magnetic field \( \vec{B} \) of strength \( (2\hat{k}) \, \text{T} \). The force acting on the charge is \( x \hat{i} \, \text{N} \). The value of \( x \) is _____.