Is command and control the best way to increase the supply of ventilators?

President Trump invoked the Defense Production Act to force GM to make ventilators (WSJ, March 2020). Three questions come to my mind.

1. What process determines the price of ventilators, supply and demand, negotiations between buyers, sellers, and third-party payers and facilitators, government regulations, or some combination?
2. Which would increase supply more efficiently and quickly, an increase in the price or government command-and-control?
3. Will the government reimburse GM for their opportunity costs or treat GM and its employees as conscripts?