What does the number 18.9984 represent in the image?

image result for how many calories of energy will 20 grams of carbohydrates provide in one gram provides 4 calories

consuming the right balance of protein, carbohydrates and fat can you maintain a healthy weight and optimize your energy levels. protein and carbohydrates both contain 4 calories per gram, while fat provides 9 calories per gram.

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.