(See previous question)Again, use the 2015 federal estate tax rules in answering this question -- as opposed to the older information in your textbook. Assume that one parent died many years ago and used up his entire estate exemption at that time. In other words, "portability" does not apply. Now, the second parent has just died, and she has an estate of $20 million. Approximately how much will the federal estate tax be on her estate?