For each of the following strategies used by Microsoft to limit competition, identify whether it is a demand-side strategy, a supply-side strategy, or a deterrence strategy. 

a. In 2018, more than 80% of all desktop PCs worldwide used the Microsoft Windows operating system. 

b. Microsoft spends a large amount of resources to attract independent software developers to write programs and applications for its operating system. 

c. Microsoft was charging an average price of $40 to $60 for its operating system to PC hardware companies such as Dell and HP instead of the monopoly profit-maximizing price of $1,800.