22. 有一矩形單筋梁斷面，若鋼筋之彈性模數採用 2300000 kgf/cm²，混凝土之極限應變採用 0.004，則此單筋梁斷面之平衡鋼筋比 \(\rho_b\) 為何？
(A) \(\rho_b = \frac{0.85 f_c' \beta_1}{f_y} \left( \frac{6120}{6120 + f_y} \right)\)
(B) \(\rho_b = \frac{0.85 f_c' \beta_1}{f_y} \left( \frac{7500}{7500 + f_y} \right)\)
(C) \(\rho_b = \frac{0.85 f_c' \beta_1}{f_y} \left( \frac{9200}{9200 + f_y} \right)\)
(D) \(\rho_b = \frac{0.85 f_c' \beta_1}{f_y} \left( \frac{11000}{11000 + f_y} \right)\)