39. To construct a calibration graph for the purpose of

39. To construct a calibration graph for the purpose of determining ions in water, a standard solution with mg / ml was used. Samples in the range of 0.10 ... 0.80 ml were treated with the necessary reagents, a 0.1% solution of chromotropic acid was added, the volume was adjusted to 10.00 ml with concentrated sulfuric acid, and the optical density was measured in a three-centimeter cuvette. Received the following data:
Vst. p-ra, ml 0.10 0.20 0.40 0.60 0.80
Optical square A 0.100 0.202 0.318 0.603 0.802
An aliquot of the analyzed solution with a volume of 2.50 ml passed through all stages of the analysis, as well as the standard solution. The optical density of this solution was 0.550.
Calculate the concentration (mg / dm3) of ions in the analyzed solution (water). How many times the concentration of ions is lower than the MPC (MPC = 10.00 mg / dm3)?