Problem $2.$

$1$ point$)$ Let the position vecor be $R(t)=($:$-t,4cos(3t),4sin(3t)$:$).$ Compute the principal unit normal vector $N(t).$

A$.\frac{(\text{:}-t,4cos(3t),4sin(3t)\text{:})}{\sqrt[\phantom{2}]{145}}$

B$.\frac{(\text{:}-1,-12sin(3t),12cos(3t)\text{:})}{\sqrt[\phantom{2}]{145}}$

c$.\frac{(\text{:}0,-(36cos(3t)),-36sin(3t)\text{:})}{\sqrt[\phantom{2}]{145}}$

D$.($:$-1,-12sin(3t),12cos(3t)$:$)$

E$.($:$0,-(cos(3t)),-(sin(3t))$:$)$