Diane made 1000*15= $<<1000*15=15000>>15000 in sales because she had 1000 customers each buy a $15 book.
37% of those customers returned their books, so that means she had .37*1000= <<37*.01*1000=370>>370 returns
Each of those returns was for a $15 book, so she had 370*15= $<<370*15=5550>>5,550 in returns
For her total leftover income, we subtract the returns from the sales and end up with 15000-5550= $<<15000-5550=9450>>9450 in income.
#### 9,450