I. Introduction
Recent years have witnessed crowdfunding [1] emerging as an effective funding mechanism to develop innovative small projects and products. Instead of relying on large investors, the objective of crowdfunding is to collect enough investment from a large crowd of contributors, where each individual (contributor) pledges a small amount of money, often in exchange for a future product. By interacting with these potential future customers, crowdfunding provides the creator with not only financial support but also useful early feedbacks. The crowdfunding industry is growing rapidly worldwide. For example, on one of the leading crowdfunding platforms, Kickstarter, 37,581 projects raised a total of 730 millions of US dollars in the year of 2020 alone [2].