<prompt> Human: Hi,I have PMI on my mortgage, and the bank has given me the option of paying down my loan to 75 of the original appraised value. This equates to paying somewhere between 9 and 10K. Estimating this will save me 500 a year in PMI costs, and about 500 a year in reduced interest on the lower principal. This equates to about a 10 guaranteed annual return on putting in 10K, without factoring in the change in the tax deduction which I believe will be more or less negligible. Right now, I have money sitting in a savings account making 1 but I like having the liquiditysafe feeling knowing that its there. Putting in this 10K wont break me right now, but its a huge chunk of cash being taken out of my savings. It makes me nervous even though Im well aware that I still seem to come out ahead for doing it.Seems to me that the wise move here, mathematically speaking, would be to sink the 10K in. Does anyone see any flaws with this logic? Thank you.  <response>: As long as you have an emergency fund of 3 to 6 months expenses, do it! 