The cations on an exchangeable sites of a 30 g soil were displaced by repeatedly washing by a salt and found to be 20 mg ca+2, 1.0 mg na+1, 39 mg k+1, 12 mg mg+2, and 18 mg al+3. the ph of the soil was 5.0. calculate the cec (cmolc/kg), percentage base saturation (pbs) and percent acidic saturation (pac) per kg of the soil.