Gizmo market in Freedonia is competitive. Suppose demand for Gizmos is QD(PD) = 20 - 3PD and supply of gizmos is QS(PS) = -3 2PS where quantity is in thousands of units per year and price is in dollars. If the government imposes a 1 excise tax on gizmos in Freedonia then what is the government's annual revenue from this tax? a) 5 thousand dollars b) 6 thousand dollars c) 4 thousand dollars d) 7 thousand dollars