$\cos \theta = \dfrac{2.6}{2 + 1}$
$\theta = 29.93^\circ$
From the FBD of 200 kN cylinder
$\Sigma F_V = 0$
$R_C \sin \theta = 200$
$R_C \sin 29.93^\circ = 200$
$R_C = 400.85 \, \text{ kN}$ answer
$\Sigma F_H = 0$
$R_D = R_C \cos \theta$
$R_D = 400.85 \cos 29.93^\circ$
$R_D = 347.39 \, \text{ kN}$ answer
From the FBD of 400 kN cylinder
$\Sigma F_H = 0$
$R_A = R_C \cos \theta$
$R_A = 400.85 \cos 29.93^\circ$
$R_A = 347.39 \, \text{ kN}$ answer
$\Sigma F_V = 0$
$R_B = 400 + R_C \sin \theta$
$R_B = 400 + 400.85 \sin 29.93^\circ$
$R_B = 600 \, \text{ kN}$ answer