Suppose you are investigating the cell cycle using two new drugs that each specifically targets one of the two subunits of MPF, cyclin B and CDK1. Interestingly, you find that upon addition of the cyclin B inhibitor, all cells eventually arrest in G2, independent of the stage in the cell cycle they were in at the time of drug addition. In contrast, the CDK inhibitor halts the cell cycle at whatever stage they were in upon inhibitor addition. Explain how two drugs that inhibit the same protein kinase complex (MPF) could affect the cell cycle so differently