Indicate whether the demand for the good would become more elastic or less elastic after each of the following changes. (Note that in each of these cases, the demand curve may also shift inward or outward, but in this question we are interested in whether the demand becomes more or less elastic.) Briefly justify your answer.

a. The demand curve for soap after wide understanding that bacteria and other organisms cause and spread disease

b. The demand curve for coal after the invention of nuclear power plants

c. The demand curve for cars as more employers allow employees to telecommute

d. The demand curve for a new television during an economic boom.  pg69