While young, females have a fertile potential of b1.

While old, females have a fertile potential of b2.

Thus lifetime fertile potential for females is 1*b1 + s*b2.

Suppose thee is some constraints, such as:

b1 + b2 = Btotal

Where Btotal is some constant. Then what is the optimal distribution of b1 and b2?

Now suppose males exercise choice, say f1 and f2 for probability of mating with a young or old female.

Then, the realized fertility is

1*f1*b1 + s*f2*b2

Depending on what f1 and f2 are, what’s the best way to optimize the distribution of b1 and b2?