$20-$ For the wing$-$tail configuration below. Given that the wing incidence angle is zero and the tail has a symmetric airfoil section. Assume that the down$-$wash angle is zero and that the dynamic pressure of the tail is equal to the dynamic pressure of the wing $[9$ points$]$

a$-$ Write an expression for the lift coefficient of the total configuration $[1$ point$]$

b$-$ Write an expression for $C_{Lo}$ and $C_L$ of the configuration $[1$ point$]$

c$-$ Write an expression for the moment coefficient about the center of mass of the configuration $[1$ point$]$

d$-$ Write an expression for $C_{mo}$ and $C_m$ of the configuration $[1$ point$]$