A Sub-20 5K

Two miles (7:02 and 6:34) solo in the cold this morning (28degrees).

The first mile is always slow. I am trying to figure out why. Maybe I
just need to warm up.

To get under 20 minutes, I would need to run the last 1.1 miles in 6.26 which is 5:51 pace.
Ouch, that won't work. I won't get to a sub-20 5K by starting out with 7:02 and 6:34.

Say I ran the whole thing at
6:30 pace. 3.1x6:30 = 1209 seconds = 20minutes 9 seconds.
6:27 pace 3.1x6:27 = 1199 seconds = 19minutes 59.7 seconds.

I think I can do this (especially on a flat run).