IUPAC name of following hydrocarbon \( (X) \) is:
\( 2 \)-Ethyl-\( 3,6 \)-dimethylheptane
\( 3,4,7 \)-Trimethyloctane
\( 2 \)-Ethyl-\( 2,6 \)-diethylheptane
\( 2,5,6 \)-Trimethyloctane