Step 1 :Define the outcomes and their probabilities. The outcomes are 400, 600, and -700, with probabilities of 0.2, 0.7, and 0.1 respectively.
Step 2 :Calculate the expected gain or loss by multiplying each outcome by its probability and summing the results. This can be represented as \( \sum \text{{outcome}} \times \text{{probability}} \).
Step 3 :The result of the calculation is 430.0, which means there is an expected gain of 430 employees next year.
Step 4 :\(\boxed{\text{{B. There is an expected gain of 430 employees.}}}\)