Transfer of 5 people from A to B:
When 5 people are transferred from A to B, it means that the population of B increases by 5 while the population of A decreases by 5. Let's assume that the initial average population of B before the transfer is X.

Transfer of 5 people from B to A:
After the first transfer, another set of 5 people are transferred back from B to A. This means that the population of B decreases by 5 while the population of A increases by 5. Now, let's assume that the average population of A after the first transfer is Y.

Effect on B's average:
To determine the effect on B's average, we need to compare the initial average population of B (X) with its population after the transfers.

Calculating the final average population of B:
1. Initial average population of B: X
2. Population of B after the first transfer: X + 5 (increase of 5 people)
3. Population of B after the second transfer: X + 5 - 5 = X (population returns to initial value)

Therefore, the final average population of B remains the same as the initial average population, which is X.

Explanation:
The transfer of 5 people from A to B and then back from B to A has no effect on the final average population of B. This is because the initial average population of B is restored after the second transfer. The transfers simply result in a temporary change in the population distribution between A and B, but the overall average of B remains unaffected.

Conclusion:
After the transfer of 5 people from A to B and another set of 5 people from B to A, the average population of B remains the same as its initial average. The transfers only cause a temporary change in the population distribution between A and B.