From the solution of Problem 243:
$R_1 = 25(2.10)/2.70$
$R_1 = 19.44 \, \text{kN}$
$R_2 = 50(0.90)/2.70$
$R_2 = 16.67 \, \text{kN}$
$R_A = R_1 + R_2$
$R_A = 19.44 + 16.67$
$R_A = 36.11 \, \text{kN}$
For segment BC
$P_{BC} + 25 = R_A$
$P_{BC} + 25 = 36.11$
$P_{BC} = 11.11 \, \text{kN}$
$\sigma_{BC} = \dfrac{P_{BC}}{A} = \dfrac{11.11(1000)}{500}$
$\sigma_{BC} = 22.22 \, \text{ MPa}$ answer