How to solve This

Force $F=80kN,$

Lengths $L_1=350mm$ and $L_2=290mm,$

and cros$-$section areas $A_1=270m{m}^2$ and $A_2=560m{m}^2,$

calculate the reaction forces $R_A$ and $R_C$ in kN $,$

and the stresses ${}_{BC}$ and ${}_{AB}$ in MPa $,$

Enter your answers in the boxes below.

The answers are acceptable within a tolerance of $1$ kN for the force and $1$ MPa for the stresses.

Respect the sign conventions!