Each retarder is the optimum point to say how much concentration will provide the needed time in which the temperature at different points of the optimum retarder will vary.
retarder each have the optimum concentration to tell how much time will be required. The optimum temperature at different points of the retarder is different.
Retarder each point will be optimum to say how much concentration to timely. Which in the different temperature points optimum of retarder are different.