How to get in better running condition in 20 days?

I have to run a mile in 20 days. I'm not an active runner becuase of knee problems in the past, but I have to run a mile under 9 minutes for the college sport i'lm going to be apart of. Now i can run the mile in about 9:10 seconds, but I want to build up my stamina and get a better time. Any exercises or tips to help build my stamina?

How to get in better running condition in 20 days?
Warm Up:


2-3 laps on a track





Form Runs:


"A" skip


Hip Flexers


Butt Kicks


High Skips


High Knees


Etc...





Stretch


You pick your own stretches





Workout





Mon/Wed


3 miles


rest


2 miles


rest


1.5 miles


Stretch





Tue/Thur


1000 meters


Jog 200


1500 meters


Jog 300


1000 meters


Jog 200


Stretch





Friday


Time Trial





Take saturday and sunday to rest