Which of the following are examples of a firm experiencing positive technological change?

a. A fall in the wages JetBlue pays its mechanics leads it 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 reduces the number of days the typical worker is absent.

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.