Briefly explain whether each of the following statements describes a change in supply or a change in quantity supplied.

a. To take advantage of high prices for snow shovels during a snowy winter, Alexander Shovels, Inc., decides to increase output.

b. The success of Yeti and Hydro Flask water bottles leads more firms to begin producing water bottles.

c. When the Covid–19 pandemic arrived in the United States, production of automobiles declined from 218,800 in February 2020 to 1,700 in April 2020.