An economy's aggregate demand is represented by the equation: $AD = (c_0 + c_1(1−t)Y) + (a_0 − a_1r) + G + (X − mY)$. Consider a scenario where the government reduces the income tax rate (t) while simultaneously, the central bank increases the interest rate (r). What is the combined impact of these two policy actions on aggregate demand, assuming all other factors remain constant?