Read the original condition carefully
Department X
Factory

When information about one area is given and it is asking about another, automatically think of weighted averages.

\(w_dx_d\)+\(w_fx_f\)/n
Where w is weight, x is average, d is department, f is factory, n is total number of workers

1) Gives \(x_d\), but not the others. Insufficient
2) Gives \(x_f\), but not the others. Insufficient.

Together, insufficient.
E

Also the difficulty of knowing whether to include department workers in the factory total. Probably should.

In this example, doing it without inclusion for simplicity
1 worker in department, 99 in factory
\(\frac{(15,000+99·20,000)}{100}\) = 19,950

99 workers in department, 1 in factory
\(\frac{(99·15,000+20,000)}{100}\)=15,050


Bunuel do you write these questions?