Workout

Warm-up (1000)
4 x 250
...100 drill, 100 kick, 50 swim
...reverse IM order

Set (900)
4 x 100 on 1:45 (build to steady pace) 
50 EZ 
4 x 100 on 1:45 (solid - controlled harder pace) 
50 EZ 

Set (300)
6 x 50’s choice on 1:30 
...odd -moderate
...even -FAST  
   
Set (200)
4 x 25 SPRINT on 1:00

Cool-down-down (200)
200 EZ