AMC 12B 2003 Problem 17

If \log \left(x y^{3}\right)=1 and \log \left(x^{2} y\right)=1, what is \log (x y) ?

Answer Choices
A. -\dfrac{1}{2}
B. 0
C. \dfrac{1}{2}
D. \dfrac{3}{5}
E. 1