In Exercises $7-12,$ find the work done by force $\mathbf{F}$ from $(0,0,0)$ to $(1,1,1)$ over each of the following paths (Figure 16.21$)$ :
a. The straight-line path $C_{1} : \mathbf{r}(t)=t \mathbf{i}+t \mathbf{j}+t \mathbf{k}, \quad 0 \leq t \leq 1$
b. The curved path $C_{2} : \mathbf{r}(t)=t \mathbf{i}+t^{2} \mathbf{j}+t^{4} \mathbf{k}, \quad 0 \leq t \leq 1$
c. The path $C_{3} \cup C_{4}$ consisting of the line segment from $(0,0,0)$ to $(1,1,0)$ followed by the segment from $(1,1,0)$ to $(1,1,1)$
$$
\mathbf{F}=\sqrt{z} \mathbf{i}-2 x \mathbf{j}+\sqrt{y} \mathbf{k}
$$