Evaluate the line integral $\int_C \mathbf{F}\cdot d\mathbf{r}$, where $\mathbf{F}(x,y,z) = -3 \sin x \mathbf{i} + \cos y \mathbf{j} - 3x z\mathbf{k}$ and C is given by the vector function $\mathbf{r}(t) = t^6 \mathbf{i} - t^5 \mathbf{j} + t^4 \mathbf{k}$ , $\quad 0 \le t \le 1$.