Draw accurate rate and stock (level) graphs that represent the following equations R stands for Rate Equation and Initial Stock in both cases is 0. - R = 5 + Step (-7,5) + Ramp (-1,10) This equation can be explained as follows : The initial value of the rate from time=0 is 5, at time =5, the rate steps down to 7 and then ramps to 1 at time = 10. - R = Step (20,5) + Step (-40,10) + Step (20,15)