Write down the change equation for this system. Indicate what each term represents and include the units for each term. Exercise C. Consider the mass-spring systeln described on pp. 32-34 in the textbook. We want to determine the model for the massspring system with friction. Suppose that a > 0 is a positive constant. Based on the description in the textbook, which one of the following models describes the massspring system with friction? Explain your reasoning. i) X'=Vand l2": XlV ii) X' = V and V' : x + t\" iii) X' = V and V' iX + X m H lav :x: | iv '3'\" IN- iv) X' = V and V' v) X\" = V and V' ix svz 1'\" 1'\". vi) X\" = V and V' = ix x \"I m