Problem $14.$ Use known area formulas to evaluate the integrals

$($a$){\displaystyle \underset{-3}{\overset{3}{}}}\sqrt[\phantom{2}]{9-x^2}dx$

$($c$){\displaystyle \underset{0}{\overset{b}{}}}4xdx,b>0$

$($b$){\displaystyle \underset{-2}{\overset{1}{}}}|x|dx$

$($d$){\displaystyle \underset{-1}{\overset{1}{}}}(1+\sqrt[\phantom{2}]{1-x^2})dx$