Which of the following are examples of a firm experiencing positive technological change?
a. A fall in the wages it pays its mechanics leads United Airlines to lower its ticket prices.
b. A training program makes a firm's workers more productive.
c. An exercise program makes a firm's workers healthier and more productive.
d. A firm cuts its workforce and is able to maintain its initial level of output.
e. A firm rearranges the layout of its factory and finds that by using its initial set of inputs, it can produce exactly as much as before.