Problem
Read the article "Contamination and washing of cloth masks and risk of infection among hospital health workers in Vietnam: a post hoc analysis of a randomised controlled trial" by Chandini Raina MacIntyre , Tham Chi Dung, Abrar Ahmad Chughtai, Holly Seale and Bayzidur Rahman and answer those 3 questions:
a) What makes this a valuable study?
b) What is the limitation of this study, if any? If so, why were they not able to address the weakness?
c) What does this article teaches people?