$($GRADED $3$ points$)=\{a,b\}$ Construction technique for compliment

Describe the construction technique that is used for the following:

From a dfa that has been constructed for language

how would one construct the dfa for $\frac{?}{\text{b}\text{a}\text{r}}(L),($the complement of $L)$

$($GRADED $3$ points$)=\{a,b\}$ Construction technique for union

Describe the construction technique that is used for the following:

From $2$ dfas that have been constructed for and $L_2,L2((a{b}^{*}aa))$

how would one construct the union of $L_1$ and $L_2.$ If needed please draw it