00:01
Hi there, so for this problem we are given the following expression and this m of t is the average 30 -year fixed mortgage rate in the united states in the first week of may in 2010.
00:16
Now, the time is in years and time equals to zero corresponds to the first week of may in 2010.
00:22
Now, you already answered part a, so let me just put in here this function 55 .9, then this divided by the time s squared, then this minus 0 .31 times the time, and then this plus 11 .2.
00:44
So, let's do part b.
00:46
Now, the question for part b is how fast was the 30 -year fixed mortgage rate decreasing? so, we already know that this should be negative because we are told that it's decreasing in the first week of may in 2011.
01:01
So, then this evaluated at one, at a time equals to one.
01:05
So, let's take first the derivative of the expression that we are given...