Total of 2 rounds (12min AB & 12min Skillmill):

3x
1min Assault bike (moderate)
1min Assault bike (easy)

Then
50 Abmat sit-ups
50 Back ext.

Rest 2min

3x
1min Skillmill run (moderate)
1min Skillmill run (easy/walk)

Then
50 Abmat sit-ups
50 Back ext.

Rest 2min