Consider a jet transport airplane with the following specifications: Lift curve slope for wing-body ∂C_wb/∂α_wb = 0.1/deg, Lift curve slope for tail ∂C_Lt/∂α_t = 0.068/deg, Tail area S_t = 80 m², Wing area S = 350 m², Distance between mean aerodynamic centers of tail and wing-body l_t = 28 m, Mean aerodynamic chord c̄ = 9 m, Downwash ε = 0.4α, Axial location of the wing-body mean aerodynamic center x_ac/c̄ = 0.25, Axial location of the center of gravity x_cg/c̄ = 0.3. All axial locations are with respect to the leading edge of the root chord and along the body x-axis. Ignore propulsive effects. The pitching-moment-coefficient curve slope (C_mα) is _______ /deg. (round off to three decimal places)