The distribution of the time until a Web site changes is important to Web crawlers that search engines use to maintain current information about Web sites. The distribution of the time until change (in days) of a Web site is approximated in the following table.

Days until Changes               Probability

1.5…………………………………...0.05

3.0…………………………………...0.25

4.5…………………………………...0.35

5.0…………………………………...0.20

7.0…………………………………...0.15

Calculate the probability mass function of the days until change.