add rules for assign Flexi task

i use Flexi Assign Task in workflow with have 3 outcomes as

• release
• assign to accountable
• assign to responsible 

and 2 field people person as

• Accountable
• Responsible

now in task form  when user select assign to accountable another field is disabled if select assign to Accountable field disabled.

how can i write a rule for it condition? how can i find value of outcomes?