Final answer:
Monopolistically competitive firms can increase product demand by establishing a good reputation, offering money-back guarantees, and investing in research and development.
Step-by-step explanation:
Monopolistically competitive firms can increase demand for their products through various strategies. One strategy is to establish a good reputation by consistently providing high-quality products. When buyers trust the firm's reputation, they are more likely to purchase the product and recommend it to others. Another strategy is to offer a money-back guarantee, which assures buyers of the product's quality and encourages them to try it without hesitation. Additionally, firms can invest in research and development to continuously improve their products and make them more appealing to customers.