According to the biot-savart force law and the right hand rule, if a magnetic field is directed rightward (+ x axis) and a positive test charge moves through the field downwards (- y axis), which direction will the magnetic force be applied onto the charge? 1. upwards (+ y axis) 2. leftward (- x axis) 3. out of the screen (+z axis) 4. into the screen (- z axis)