$($Table$)$ Based on the table, at what wage rate is the supply curve backward bending?

$\backslash$table$[[$Labor Supply Schedule,$],[$Wage Rate $($$$/$hr$.),$Hours of Work $($per week$)],[20,30],[30,40],[40,50],[50,40],[60,30]]$

$$ after $$20$ per hour

$$ after $$30$ per hour

after $$40$ per hour

after $$50$ per hour