In an isotope dilution experiment, chloride was determined by adding 5.0 mg of sodium chloride containing 38CI (t1/2 = 37.3 min) to a sample. The specific activity of the added NaCl was 4.0 X 104 cps/mg. What was the total amount of chloride present in the original sample if 400 mg of pure AgCI was isolated and if this material had a counting rate of 35 cps above background 148 min after the addition of the radiotracer?