A goal programming problem had two goals $($with no priorities assigned$).$ Goal number $1$ was to achieve a cost of $$3,600$ and goal number $2$ was to complete the task in $400$ hours or fewer. The optimal solution to this problem resulted in a cost of $$3,600$ and a completion time of $420$ hours. What was the value for the objective function for this goal programming problem?

Question $30$ options:

$400$

$-400$

$20$

$0$

None of these