Use the Comparison Test or Limit Comparison Test to determine whether each series is convergent or divergent. Carefully show your work and justify your conclusion.

$($a$){\displaystyle \underset{k=1}{\overset{}{}}}\frac{4k^2-k}{k^{3}k1}$

$($b$){\displaystyle \underset{k=0}{\overset{}{}}}\frac{1cosk}{8^k}$

$($c$){\displaystyle \underset{k=1}{\overset{}{}}}\frac{1}{k^{2}arctan(k)}$