A scientist has two kinds of solutions. The first solution is Solution A, which is an $80\%$ acid solution. The second solution is Solution B, which is a $30\%$ acid solution.
(a) Find the amount of Solution A (in mL) that must be added to $500$ mL of Solution B in order to produce a $70\%$ acid solution.
(b) Find the amount of Solution A and Solution B (in mL) that can be combined in order to form a $100$ mL solution that is $50\%$ acid.
(c) Does there exist a combination of Solution A and Solution B that is $90\%$ acid?
i already know a and b i neeed help with (c)