Matrices problem

Let $\mathbf{P}$ and $\mathbf{D}$ be the following $3\times 3$ matrices:

$\begin{align*} &\mathbf{P} \text{ projects vectors onto $\begin{pmatrix} 1 \\ 2 \\ 4 \end{pmatrix}$},\\ &\mathbf{D} \text{ dilates vectors by a factor of $3.$}\\ \end{align*}$

Calculate the matrix $\mathbf{D} \mathbf{P} \begin{pmatrix} 1 & 0 & 2 \\ 2 & 0 & 1\\ 4 & 0 & -1 \end{pmatrix}.$