Suppose that you are going to program a computer to carry out an iterative calculation of motion involving nonconstant forces. Which of the following calculations should be done before starting the repetitive "loop" calculations? Specify the initial (vector) momentum of each object. Calculate the (vector) forces acting on the objects. Specify an appropriate value for the time step. Update the (vector) position of each object. Specify the mass of each object. Define constants such as G. Update the (vector) momentum of each object. Specify the initial (vector) position of each object.