Number of words: 252
Time: 4.5 minutes
To find the unit rate r in words per minute, we use the formula:
[tex]r=\frac{W}{t}[/tex]Where W is the number of words, and t is the time elapsed. Using the information of the problem:
[tex]r=\frac{252}{4.5}=56\text{ words per minute}[/tex]