Answer and explain your choice. I will rate accordingly with multiple votes. Ty-ped answer only.....

The optimal amount of consumption of goods and leisure is given by the point where the budget line is tangent to the indifference curve. This is an interior solution because the worker is not at either corner of the opportunity set. In which case will the solution not be an interior solution but a corner one? Q) When indifference curves are concave Q When the indifference curves intersect each other but are convex Q When the indifference curves are downward sloping