Given the hyperbola $\frac{y^2}{100}-\frac{x^2}{139}=1$, find the length of the $a$-axis and the $b$-axis.

• A. $a=100,b=139$
• B. $a=139,b=100$
• C. $a=\sqrt{139},b=10$
• D. $a=10,b=\sqrt{139}$