A researcher used a normal distribution with mean a of 150 and SD of 15 as a prior for the values of a parameter. The observed data was 100, and the likelihood has the shape of a normal distribution with a mean of 100 and SD of 15. Which of the following statements is the most likely posterior distribution?

1. A normal distribution with a mean of 150.
2. A normal distribution with a mean of 15.
3. A normal distribution with a mean of 125.
4. A normal distribution with a mean of 100.
5. A standard normal distribution.