Let the function $f$ be defined as $f(x)=c\left(3\cdot 3^x+3^d\right)$, where $c$ and $d$ are integer constants with $0<c<d$. Now, consider the functions $p(x)=c(3^x+l)$ and $q(x)=c(3^x)+n$, where $l$ and $n$ are constants. Which, if any, of these functions expresses the y-coordinate of the y-intercept of $y=f(x)$ in the $xy$-plane as a constant or coefficient?