4. Consider an investigation into the effect of the concentration of the reactant and the amount of the catalyst on the conversion (yield) in a chemical process. Let the reactant concentration be factor A and let the two levels of interest be 15% and 25%. The catalyst is factor B, with the high level denoting the use of two pounds of the catalyst and the low level denoting the use of only one pound. The experiment is replicated 3 times, and the data are as follows: Replicate || III abo 28 25 27 80 a.bo 36 32 32 100 ab 18 19 23 60 ab 31 30 29 90 a. Explain the average effect of the factor A. b. How does the above differ from "a"? c. Explain the interaction effect AB. d. Explain the concept of contrast of means, treatment effects or treatment combinations.