Final answer:
Sony did use penetration pricing when it launched the Walkman personal stereo in 1979.
Step-by-step explanation:
Penetration pricing is a pricing strategy in which a company sets a low initial price for its product in order to gain market share quickly.
In the case of the Sony Walkman personal stereo, it launched in 1979 at a price of $150, which was relatively low compared to other portable audio cassette players on the market at the time. This low price helped Sony quickly establish a strong position in the market and attract a large number of customers.