Final answer:
The correct formula to calculate lambda (λ) depends on the context which is not provided. Without context, it is not possible to definitively choose between mathematical operations of addition, multiplication, or division as indicated in the options A, B, C, or D.
Step-by-step explanation:
To calculate lambda (λ), which typically represents a constant rate of change, the correct formula must be chosen based on context. The provided variables of 'age', 'cohort', and 'bx' sound like they are related to a social studies or demographic study, specifically when dealing with life expectancy or some similar metric. However, without explicit context, these formulas could technically apply to various mathematical scenarios, but not with literal interpretation of 'age' or 'cohort' as demographic terms.
The formula given by the student appears to represent a linear equation, where λ is the dependent variable. The formulas are structured to suggest relationships between the variables, and their selection depends on how these variables interact with one another. For a direct computation of λ without further context, any of the provided equations could be a mathematical expression, but we would need to know the specific context in which these variables are being used to determine which operation (addition, multiplication, division) is appropriate.
Since this question comes without a clear field of application, it's recommended to seek additional context to accurately determine the formula to use for calculating λ. Without the context, it is impossible to offer a definitive answer to which option (A, B, C, or D) is correct.