urgent help please

Using the 68-95-99.7 Empirical Rule-of-Thumb, answer the following questions. No partial credit will be given for using any other method.

Students who had a low level of mathematical anxiety were taught using the traditional expository method. These students obtained a mean score of 450 with a standard deviation of 30 on a standardized test. The test scores follow a normal distribution.

a. What percentage of scores would you expect to be greater than 420?

b. What percentage of scores would you expect to be less than 510?

c. What percentage of scores would you expect to be between 420 and 510?