Write the structural formulas of the following compounds:
$(i)$ $3,4,4,5-$Tetramethylheptane
$(ii)$ $2,5-$Dimethylhexane

(N/A) $(i)$ The parent chain is heptane ($7$ carbons). Substituents are four methyl groups at positions $3, 4, 4,$ and $5$. The structure is: $CH_3-CH_2-CH(CH_3)-C(CH_3)_2-CH(CH_3)-CH_2-CH_3$
$(ii)$ The parent chain is hexane ($6$ carbons). Substituents are two methyl groups at positions $2$ and $5$. The structure is: $CH_3-CH(CH_3)-CH_2-CH_2-CH(CH_3)-CH_3$