According to Raoult's law, how does the presence of a nonvolatile solute B affect the vapor pressure of a liquid solvent A?

Raoult's law states that the vapor pressure of a solvent in a solution is directly proportional to the mole fraction of the solvent. This can be expressed as: $P=X{P}_0$, where $P$ is the vapor pressure of the solvent in the solution, $X$ is the mole fraction of the solvent, and $P_0$ is the vapor pressure of the pure solvent.