The melting point of pure A is 120°C and that of B is 110°C. The upper curves connecting points A with E and E with B are the boundary above which mixtures of A and B of any composition are completely melted. The lower horizontal line through point E is a boundary representing the temperature (99°C) below which the sample is completely solid at any composition. In the areas between these phase boundaries are mixtures of one or the other pure solids plus liquid.