1.3.2.3b - use formulae to calculate price, income and cross-elasticities of demand

How to use formulae to calculate price, income and cross-elasticities of demand.

Use b - use formulae to calculate price, income and cross-elasticities of demand to connect the rule to the data and decision in the question.

This matters because b - use formulae to calculate price, income and cross-elasticities of demand determines what can be inferred or chosen; begin with the stated conditions and keep the conclusion tied to the evidence.

Example: apply b - use formulae to calculate price, income and cross-elasticities of demand to one small, clearly defined case, show the key step or comparison, and explain the result in words.

Boundary: use the formula and units given in the question, show the substitution and interpret the result; the calculation alone is not the conclusion.