I was wondering under what set of conditions one is allowed to assume an interior solution to the Utility Maximisation Problem. In most of my classes and lecture notes, interior solutions are assumed from the outset.
Intuitively, it seems to me that if the utility function is:
- monotone (increasing in all its arguments)
- strictly quasi-concave (implying strict convexity of indifference curves)
we are guaranteed an interior optimum. Is this correct? Thank you in advance!