Chapter 12.4, Problem 3QCE

If C is the graph of a smooth vector-valued function $\text{r}\left(t\right),$ then the unit binormal vector to C at t may be compute directly in terms of $\text{r}\text{'}\left(t\right)\text{and}\text{r''}\left(t\right)$ by the formula $\text{B}\left(t\right)=\text{\_\_\_\_\_\_\_\_}\text{.}$ When $t=s$ is the arc length parameter, this formula simplifies to $\text{B}\left(s\right)=\text{\_\_\_\_\_\_\_\_}\text{.}$