P = 0.75m represents the proportional relationship, therefore, the profit earned for each muffin sold is: $0.75.
If two variables, i.e. P and m are directly proportional to each other, the relationship between them can be represented as P = km, where k is the constant.
Given that P = 0.75m represents the proportional relationship between the profit earned and muffins sold, the constant, k, is 0.75, which is the profit earned for each muffin sold.
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