作为垄断者有三种不同的定价策略：纯捆绑销售、单独销售和混合捆绑销售。比较这三种定价策略，找出垄断者的最优策略
As a monopolist, it has three alternative pricing strategies: pure bundling, selling the good separately and mixed bundling. Please try to compare these three pricing strategies and find the optimal strategy for the monopolist.