Problem $1$a$.$ Using the displacement method determine $($by hand calculation$)$:

a$.$ the nodal displacements;

b$.$ the reactions;

c$.$ the internal forces in the elements;

d$.$ the maximum axial stress.

Input data: $E=1$;$A=1$;$l=1$;$F=1.$

Problem $1$b$.$ For the given pin$-$jointed framework $($verso$),$ determine the location and the value of: $a.$ the maximum nodal displacement; $b.$ the maximum axial stress.