A Soil Has a Maximum Potential Cation Exchange Capacity of 30

Multiple Choice

A soil has a maximum potential cation exchange capacity of 30 cmol_c/kg and has a 50% acid saturation.If you want to decrease the percentage acid saturation to 10%,how many cmol_c of calcium would it take to replace the exchangeable acid cations per kg of soil? Assume all the calcium exchanged with aluminum.

A) 30
B) 40
C) 6
D) 12
E) 5