Subsidy costs, new equilibrium with the demand curve, economics graph homework help

Graph of straight-line supply and demand curves that intersect at (800, $40). The supply curve has y-intercept at $120 and x-intercept at 1200. The demand curve has y-intercept at 0 (the origin). If you shift the supply curve up vertically by $30 the new equilibrium with the demand curve would occur at (600, $60)” ;

I like this old school graph… look at it carefully. A $30 per unit production subsidy would cost how much to taxpayers?