Need some tax advice re annuities.

[TNDemo]

My mother died last year and was receiving a monthly payment from a small annuity. After she died I received it for the remainder of the year. I have been sent a 1099-R for the amount I received and it states on it that I need to determine whether or not it is taxable. So for line 16 on the 1040 it had a table to determine how much is taxable. All the questions seem to related to the annuitant - age, etc. I can't seem to find something that says "if you inherited this." I am thinking that probably the whole amount is taxable for me but want to make sure. I e-mailed the IRS, who sent back an automated response saying to look on-line at the instructions for the 1040 and for further questions call them on Monday. Any tax experts here who know the answer?