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