I am learning statistics from this book and in Exercise 2.27 (on page 79) I came across the term unimodal. As I understand, unimodal means having only one value of mode. But in this question, in part (b), it is asked to give an example of unimodal PDF in which mode is not unique. So how can a PDF be unimodal when its mode is not unique? Or, have I misunderstood something here? Please explain.