Which sentence is correct?

I'm writing a technical paper. However, I am not sure which one of the following sentences is correct:

1. When A is less than B, the gains of optimizing the power are minimal for case C and marginal for case D.

2. When A is less than B, the gain of optimizing the power is minimal for case C and is marginal for case D.

3. When A is less than B, the gain of optimizing the power is minimal for case C and this gain is marginal for case D.

Can anyone tell me? Many thanks in advance.