Step-by-step explanation:
The substance A and B will mix into one solution as it is a solvent interactions which is greater than or equal to the solute- solute and the solvent-solvent interactions. Thus when such interactions occurs, it is greater or equal to the some of the other two possible interactions. And here both have the same kind of interaction, and same magnitude, so they will makes to form a solution and mixes properly and spontaneously.