Write the $IUPAC$ names of the following compounds:
$(1)$ $CH_3(CH_2)_4-CH(CH_2CH(CH_3)_2)-(CH_2)_3CH_3$
$(2)$ $CH_3-CH=CH-CH_2-CH=CH-CH(C_2H_5)-CH_2-CH=CH_2$

(A) $(1)$ The longest carbon chain contains $10$ carbon atoms. The substituent at position $5$ is a $2$-methylpropyl group. Thus,the $IUPAC$ name is $5-(2-methylpropyl)decane$.
$(2)$ The longest carbon chain containing the double bonds has $10$ carbon atoms. The substituent at position $4$ is an ethyl group. The double bonds are at positions $1, 5,$ and $8$. Thus,the $IUPAC$ name is $4-ethyldeca-1,5,8-triene$.