Elasticity of demand... please help

Question

here's the problem

Aztec Enterprises depends heavily upon advertising to sell its products. Management and Aztec is allowed to spend $2 million monthly or advertising, but no more than this amount. Each month, aztec spends exactly $2 million on advertising. What is aztec's elasticity of demand for advertising? Can you write the equation for Aztec's demand for advertising?

Answer 1

Advertising as a function of price can be written as A(P)=$2 million since expenditure does not depend on its own price level. In other words, demand for advertising is inelastic.

The formula for any elasticity has the form dA/dP*(P/A), but since demand for advertising in this context is inelastic, elasticity = 0 for all values of P