A sample from an effluent stream was analysed for phosphate levels. Dilute hydrochloric acid and excess sodium molybdate were added to a 50 cm³ sample of the effluent. The molybdophosphoric acid, H₃PMo₁₂O₄₀, that was formed was extracted into two 10 cm³ portions of an organic solvent. A molybdenum standard with a concentration of 10 ppm was prepared in the same solvent. The combined extract and the standard were aspirated into an atomic absorption spectrometer that was set up to measure molybdenum. The extracts gave an absorbance of 0.573 and the standard gave an absorbance of 0.222. Calculate the concentration of phosphate in the effluent.