Three point charges are placed at the vertices of an equilateral triangle with side length $a = 0.5m$. Charge $q_1 = +2.0\text{ }\mu\text{C}$ is at the top vertex, $q_2 = -4.0\text{ }\mu\text{C}$ is at the bottom-left, and $q_3 = +6.0\text{ }\mu\text{C}$ is at the bottom-right. Calculate the magnitude of the net force on $q_1$. (Given $k = 9 \times 10^9\text{ N}m^2/\text{C}^2$)