Find the matrix $A$ of the linear transformation
$T(f(t)) = \int_{-6}^4 f(t) \ dt$
from $P_3$ to $\mathbb{R}$ with respect to the standard bases for $P_3$ and $\mathbb{R}$.
$A = \left[ \ \ \color{red}{\square} \quad \color{red}{\square} \quad \color{red}{\square} \quad \color{red}{\square} \ \ \right]$
I'm a little confused about what $P_3$ stands for and where $A$ is coming from.