The question is asking which plant had 4 or more weeks with a higher unit production than the other plant.

Statement 1) this statement says that factory C produced twice as many units in total over the span of seven weeks. This doesn't tell us whether 4 or more of those weeks had levels above those at plant D.

Think about two simple scenarios,
Plant C produces 0 units in weeks 1-6 and 14,000 units in week 7. Total units = 14,000.
Plant D produces 1,000 units in each week. Total units = 7,000.

In this case, plant D produces more units in 6 out of 7 weeks, and is the more efficient plant.

The other scenario is that plant C produces 2,000 units per week and D produces 1,000 units per week. In this case plant D is the more efficient plant.

Insufficient.

Statement 2) The statement says nothing about the distribution of units produced for either plant. Insufficient.

Combined) After adding the second statement to the first, both scenarios I listed are still possible, and still yield different results for the more efficient plant. Insufficient.

IMO E