Structures and IUPAC names of some hydrocarbons are given below. Explain why the names given in the parentheses are incorrect.
`underset(["and not 3,4,7-Trimethyloctane"])underset(2,5,6- "Trimethyloctane")(CH_(3)-underset(CH_(3))underset(|)(CH)-CH_(2)-CH_(2)-underset(CH_(3))underset(|)(CH)-underset(CH_(3))underset(|)(CH)-CH_(2)-CH_(3))`
`underset(["and not 5-Ethyl-3-methylheptane"])underset("3-Ethyl-5-methylheptane")(CH_(3)-CH_(2)-underset(CH_(2)CH_(3))underset(|)(CH)-CH_(2)-underset(CH_(3))underset(|)(CH)-CH_(2)-CH_(3))`

Explanation

(i) The set of locants (2,5,6) is lower than the set of locants (3,5,7).
(ii) When substituents are at equivalent positions, lowest locant is given to that substituents which comes first in the alphabetical order. Therefore, lower locant 3 is assigned to ethyl and higher locant 5 is assigned to methyl group.