Argh, thanks, that was really simple. I'm stuck on the next question though...
Q) Albert and Bella are standing in a lift. The mass of the lift is 250kg. As the lift moves upward with constant acceleration, the floor of the lift exerts forces of magnitude 678N and 452N respectively on Albert and Bella. The tension in the cable at the which is pulling the lift upwards is 3995N.
a) Find the acceleration of the lift.
b) Find both Albert's and Bella's mass.
I
really am clueless on this question. I know it's F=ma but no idea where to go with finding the acceleration, as I can't work out the resultant force