I don't. I don't have to. Your WCF defines reprobate in direct opposition to Paul's references. Paul refers to reprobate in good works and reprobate in the faith. You guys call reprobate a state of being conferred upon an individual before time began. You guys don't get Paul - how can you possibly get Jesus?
The dictionary definition of "reprobate is...
n.rep·ro·bate
1. A morally unprincipled person.
2. One who is predestined to damnation.
And yet you wrote...
The whole WCF up until now has told us that the reprobate cannot avoid sin and cannot be saved.
Mark, no man can "avoid sin." That is not the definition of a reprobate. That is the definition of mankind.
The definition of a "reprobate" is one who will not repent and believe. Thus, by definition, a "reprobate" is one who "cannot be saved" for "everything not of faith is sin."
Now you know.