Problem $3(30$ points$)$: $($PROBLEM $11\mathrm{.}53$ from Statics and Mechanics of Materials, Beer et al$.,$ Third Edition, $2021,$ McGraw$-$Hill.$)$:

Using the relation between the load, shear and moment $($area under the curve method$),$ draw the shear and bending$-$moment diagrams for the beam and loading shown, and determine the maximum absolute value $($a$)$ of the shear, $($b$)$ of the bending moment.