Find $\int_{C}\textbf{F}\cdot d\textbf{x}$ where $C$ is the line from $\left(2,1\right)$ to $\left(4,5\right)$

Question

Find $\int_{C}\textbf{F}\cdot d\textbf{x}$ where $C$ is the line from $\left(2,1\right)$ to $\left(4,5\right)$ and $\textbf{F}=6y\textbf{i}+3x\textbf{j}$. I have set the problem up as such: \begin{align} \int_C6y\:dx+3x\:dy &=\int_2^4 \left(6\left(2t-3\right)+6t\right)\:dt\\ &=\left[9t^2-18t\right]_2^4\\ &=1296-72. \end{align} And please -- no answers, only suggestions since this is a homework problem. I'm just trying to see where I may have gone wrong.