A 50.0 ml sample containing cd²⁺ and mn²⁺ was treated with 49.9 ml of 0.0400 M EDTA. titration of the excess unreacted EDTA required 17.6 ml of 0.0200 M Ca²⁺. the cd²⁺ was displaced from EDTA by the addition of an excess of CN⁻. titration of the newly freed EDTA required 10.3 ml of 0.0200 M Ca²⁺. what are the concentrations of cd²⁺ and mn²⁺ in the original solution?
a) [Cd²⁺] = 0.020 M, [Mn²⁺] = 0.030 M
b) [Cd²⁺] = 0.030 M, [Mn²⁺] = 0.020 M
c) [Cd²⁺] = 0.015 M, [Mn²⁺] = 0.025 M
d) [Cd²⁺] = 0.025 M, [Mn²⁺] = 0.015 M