Explain whether the width of a confidence interval would increase, decrease, or remain the same as a

Question:

Explain whether the width of a confidence interval would increase, decrease, or remain the same as a result of each of the following changes:
a. The sample size is doubled, from 400 to 800.
b. The population size is doubled, from 25 million to 50 million.
c. The level of confidence is lowered from 95% to 90%.