Explain the Role of Area in the Normal Density Function $\mu = 610$

Explain the Role of Area in the Normal Density Function
-The analytic scores on a standardized aptitude test are known to be normally distributed with mean $\mu = 610$ and standard deviation $\sigma = 115$ .
(a) Draw a normal curve with the parameters labeled.
(b) Shade the region that represents the proportion of test takers who scored less than 725 .
(c) Suppose the area under the normal curve to the left of $X = 725$ is $0.8413$ . Provide two interpretations of this result.