$$\begin{cases} \vec F = q\vec v \times \vec B\\ q = 3\\ \vec v = 2.0\i + 4.0\j +6. 0\k\\ \vec F = 4.0\i - 20\j + 1 2\k\\ \vec B = B_x\i+B_y\j+B_z\k\\ B_x=B_y\\ \end{cases} $$ $$\vec F = q\vec v \times \vec B$$ $$ \begin{aligned} \vec F=&q(v_x\i+v_y\j+v_z\k)\times (B_x\i+B_y\j+B_z\k)\\ =&q\begin{vmatrix} \i & \j & \k\\ v_x&v_y&v_z\\ B_x&B_y&B_z\\ \end{vmatrix}\\ =&q\begin{vmatrix} v_y&v_z\\ B_y&..