After the imposition of the tax, producers received lower price per unit (Pp) than the price per unit which consumer pay (Pc). More specifically, Pp=0,75xPc. Thus, the cost of production is increased because Q's = 20 + 2x(0,75Pc) and the supply curve shifts upwards from Qs = 20 + 2P to Qs' = 20 + 1,5P.
The after tax situation in the market is represented diagrammatically below.
The conssequences to the different stakeholders are: