Explain the analogy of the divided line as an exemplary case of Plato’s epistemology

This question from an IB philosophy exam gives an opportunity to discuss Plato’s epistemology in books V–VII his Republic with a focus in one of its classical analogies: the divided line. Plato suggests that different levels of cognition and their objects may be mapped out along an unequally divided line. The first division of the line separates two kinds of cognition: opinion (doxa) and knowledge (gnosis), which have as their objects the visible world and the intelligible world. Only the latter constitutes true knowledge. Each of these unequal segments is then divided again. The 'opinion' section is divided into 'illusion' (eikasia) -the lowest form of cognition- and belief (pistis). The object of illusion is shadows, but the object of belief is images, such as those of the senses. The 'knowledge' section of the line is then divided into and mathematical reasoning (dianoia) and intelligence (noesis). The objects of the former are numbers and geometry, whilst those of the latter are the Platonic forms, and ultimately the Form of the Good.