Concept:The quantity supplied is found by substituting the given price into the supply equation and solving for Qs.Explanation:The supply equation is given as Qs−80−0.7P=0.Rearrange the equation to make Qs the subject:Qs=80+0.7P.Substitute P=40 naira into the equation:Qs=80+0.7(40).Qs=80+28.Qs=108 tons.Answer:A. 108 tons.