A different stereoisomer of 1-tert-butyl-4-methylcyclohexane was formed when lithium dimet...

A different stereoisomer of 1-tert-butyl-4-methylcyclohexane was formed when lithium dimethylcuprate was allowed to react with each of the compounds shown.

Give the structure of the product from each reactant. One reactant gave a higher yield of the substitution product than the other (36% versus 6%). Which one? What was the major product in each reaction?