What is the net force on an object
at rest?

-- If it's at rest, then it's not accelerating.

-- If it's not accelerating, then the net force acting on it is zero. (See Newton's 2nd law of motion.)

-4 on

  distance on the y-axis and time on the x-axis.

explanation:

the instantaneous velocity = change in position/time taken

the slope of the graph should give instantaneous velocity.

  slope of a graph = change in value of y -axis / change in values of x -axis

  comparing both the equations

    change in value of y -axis = change in position

  change in values of x -axis = time taken

so position values should be on the y axis and time values should be on the x axis.

distance on the y-axis and time on the x-axis.