[LONGITUDINAL]
input = {ka, V, Cl, k12, k21, k13, k31}

EQUATION:
k = Cl/V
ddt_Ad = -ka*Ad
ddt_Ac = ka*Ad - k*Ac + k21*Ap - k12*Ac + k31*Aq - k13*Ac
ddt_Ap = -k21*Ap + k12*Ac 
ddt_Aq = -k31*Aq + k13*Ac
C = Ac/V