PROBLEM $4(10$ points$)$: The centers of gravity of the $50$ kg lift truck and the $120$ kg box are at G $1$ and G $2,$ respectively. The truck

must be able to negotiate the $5$ mm step when pushing force P is $600$ N $.$

Calculate the normal reaction at B $,$ in N $.$

Calculate the reaction between the curb and the wheel at A$,$ in N$.$

Calculate the minimum allowable radius of the wheel at A$,$ in mm $.$