Based on M&M theory with no tax, capital structure doesn't matter due to homemade leverage. However, no tax is an assumption too strong. Luckily, this assumption can be easily relaxed which lead to M&M theory with tax. M&M theory with tax suggests: the value of the levered firm is equal to the value of the unlevered firm plus tax shield (V_L = V_u - T_c+B). Please explain why the value of tax shield = T_c+B