Throe students separately pull or push one, two, or three boxes on a smooth horizontal surface, as shown in the figure. In all cases, the acoeleration is the same. Assume that all ropes as maseless.

Case $1$

${?}_x^{\text{y}\text{u}\text{a}\text{r}\text{r}}$

In which case is the strength of the pull or push the greatest?

Greatest for Case $1$ and Case $2$ only

Care $1$

Case $2$

Greatest for Case $1$ and Case $3$ only

Grestest for Case $2$ and Case $3$ only

Case $3$

Same for all