Tom pushes a 3·5 kg box with a net force of 50 N, James pushes the same box with a net force of 75 N. Who pushes the box with the greater acceleration?

Aresistor with an unknown resistance is connected in parallel to a 9 ω resistor. when both resistors are connected in parallel to an emf source of 21 v, the current through the unknown resistor is measured with an ammeter to be 4 a. what is the resistance of the unknown resistor? answer in units of ω.