What does calculating economic value require?

$$ a$.$ A larger number of brands $($preferably $10+$ brands$)$ for which performance and price data can be obtained from a secondary source, such as Consumer Reports.

$$ b$.$ A small number of brands and a consumer survey.

O c$.$ About $5$ companies and primary sources of their financial reports.

$$ d$.2$ or more brands. The data can be collected from in$-$depth interviews and casual benchmarks.