By symmetry

$C_V = B_V = 400 ~ \text{lb}$

$\Sigma M_A = 0$

$8B_H = 6B_V + 8(500)$

$8B_H = 6(400) + 8(500)$

$B_H = 800 ~ \text{lb}$

From Member *CB*

$\Sigma F_H = 0$

$C_H = B_H = 800 ~ \text{lb}$

$P_a = 800 ~ \text{lb}$

$M = 400(5) = 2000 ~ \text{lb}\cdot\text{ft}$

$\sigma_t = \dfrac{P_a}{bd} + \dfrac{6M}{bd^2}$

$\sigma_t = \dfrac{800}{4(4)} + \dfrac{6(2000)(12)}{4(4^2)}$

$\sigma_t = 2300~ \text{psi}$ *answer*