Making a decision about technology requires economic information about relative prices?the cost of hiring a worker relative to that of purchasing a tonne of coal.

The firm can calculate the cost of any combination of inputs that it might use by multiplying the number of workers by the wage and the tonnes of coal by the price of coal. We use the symbol w for the wage, L for the number of workers, p for the price of coal and R for the tonnes of coal:

cost = (wage x workers) + (price of a tonne of coal x number of tonnes) = (W X L) + (p x R)