A:
900 warm up 3x(200 swim, 50 kick, 50 drill)
12x50 @ :50 (descend stroke count 1-4, 5-8, 9-12)
main set:
5x400 @ 5:20-6:00 interval
(#1, 3, 5: swim, descend 400 times)
(#2, 4: pull, negative split effort)
8x50 @ :55 (IM Switch: fly/back, back/breast, breast/free, free/fly)
200 cool down
*4100 Total*

Optional set before cool down:
5x100 @ 1:40 (50 cruise, :5 rest, 50 FAST)
*4600 Total*

B:
600 warm up 2x(200 swim, 50 kick, 50 drill)
8x50 @ :50 (descend stroke count 1-4, 5-8)
main set:
5x300 @ 5:30-6:00 interval
(#1, 3, 5: swim, descend 300 times)
(#2, 4: pull, negative split effort)
8x50 @ 1:10 (3/5 breathing pattern by 25)
200 cool down
*3100 Total*

C:
300 warm up (200 swim, 50 kick, 50 drill)
8x50 @ 1:20 (descend stroke count 1-4, 5-8)
main set:
5x200 @ 4:30-5:00 interval
(#1, 3, 5: swim, descend 200 times)
(#2, 4: pull, negative split effort)
8x50 @ 1:30 (3/5 breathing pattern by 25)
100 cool down
*2200 Total*