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An ammonia analysis performed on a wastewater sample yielded 7 mg/L as nitrogen. The value reported is the sum of both forms of ammonia (NH3) and ammonium (NH4+) and is reported as total ammonia or simply - ammonia. If the pH of the sample was 7.4, determine the ammonium concentration (mg/L) in the sample assuming a temperature of 25C. Enter your final answer with 2 decimal places