Answer
$0$
Work Step by Step
Work done $=\int_a^b F(r(t)) \dfrac{dr}{dt}(dt)$
and $ \dfrac{dr}{dt}=\cos t i-\sin t j +\dfrac{1}{6} k$
Then work done $=\int_0^{2 \pi} \cos t -\cos^2 t\sin t+2 \sin t dt$
or, $=[\sin t+(1/3) cos^3 t-2 \cos t ]_0^{2 \pi}$
or, $=0$