Mary died on April 3, 2013. As of this date, Mary's gross estate was valued at $6.5

Question:

Mary died on April 3, 2013. As of this date, Mary's gross estate was valued at $6.5 million. On October 3, Mary's gross estate was valued at $5.8 million. The estate neither distributed nor sold any assets before October 3, 2013. Mary's estate had no deductions or adjusted taxable gifts. What was Mary's lowest possible estate tax liability?