X is normally distributed with mean $\displaystyle \mu$ where the mean is greater than zero

If $\displaystyle Pr(a>X)=0.025$

what is the closest decimal approximation for the value

$\displaystyle Pr(-a<X<\mu)$???

a:0.025

b:0.05

c:0.475

d:0.4875

e:-0.025 (obviously wrong choice, just provided for question completeness)