Estimating $\sum\limits_{n\leq x} d_3(n)$.

Question

If $d_3(n)$ denotes the number of ways to write $n$ as a product of $3$ positive integers then how do I show that as $x\to \infty$, $\sum\limits_{n\leq x}d_3(n)=\frac{x(\log x)^2}{2}+O(x\log x)$. Further how to refine this to obtain a secondary main term of the form $cx\log x$ for some constant $c$ and an error term $o(x\log x)$??