A laboratory analysis showed that a silt loam soil contained 4 meq Na+/per 100g soil. Soil pH = 8.7 and CEC = 15 meq/100g soil. The exchangeable K+ percent is 4%. What is the ESR of this soil? Determine the amount of CaSO4·2H2O needed to reduce the exchangeable Na+ to 5% in the surface foot of soil.