The diagram shows a cylinder of radius $R$ that carries a charge that is uniformly distributed throughout its volume. The cylinder has a charge *per unit length* of $\lambda$.

A Gaussian surface is imagined that is also shown in the diagram. This Gaussian surface is also a cylinder having the same axis as the charged cylinder. The Gaussian cylinder's radius is $a$, where $a < R$, and its length is $L$.

What is the charge enclosed in the Gaussian cylinder?