Final answer:
The price elasticity of demand for radios is unit elastic, which means the percentage of quantity demanded changes at the same rate as the price change. Therefore, the total revenue from radio sales will remain unchanged.
Step-by-step explanation:
When the price of radios decreases by 5%, and the quantity demanded increases by 5%, the price elasticity of demand for radios is unit elastic. This is because the percentage change in demand is exactly the same as the percentage change in price. In such a case of unitary elasticity, the total revenue from radio sales will remain the same. This scenario is described by the principle that if elasticity is 1, the total revenue is already maximized, and the advisable action for the company would be to maintain its current price level.