Calculate Consumer Surplus

"Try these formulas to calculate consumer surplus:CS = (bc+ad) x (a-((a-c)/(b+d))) / (2(b+d))PS = (bc+ad) x (((a-c)/(b+d))-c) / (2(b+d))But problem might be if c<0 , then P axis intersection by supply curve will be below zero and this part shouldn't be counted as surplus.P.S. Best way how to test is take some sample demand and supply curves and calculate with real numerical values but not in .