I. $(25$ points$)$

as problem I on Exam $1,$ except now there's friction!!! Three boxes $($with masses $m_1,m_2,$ and $m_3,$ as shown in the diagram$)$ are on a flat surface with coefficient of kinetic friction ${}_k,$ and are connected with two massless ropes. You pull on a third rope, giving it a force $T_3$ at an angle $$ above the horizontal, and the three boxes move to the right $($all with the same acceleration$).$ The tensions in the two ropes connecting the boxes are $T_1$ and $T_2.$

I. $1(9$ pts$)$ Draw three separate free$-$body diagrams, one for each box. Label all forces.

I. $2(8$ pts $)$ Find the magnitude of the total frictional force that the floor exerts on all three boxes. For parts $L_2$ express your answers in terms of the variables $m_1,m_2,m_3,T_3,,g,$ and ${}_k.($You don't have to use all these variables in each answer, but your answer should include only these variables and no others.$)$

I. $3(8$ pts $)$ Find the acceleration of the boxes $($just one answer$).($And see above.$)$