Update README.md

labs/lab1-parallel-box-blur-filter/README.md

@@ -59,7 +59,7 @@ By the time you are finished with this assignment, you will:
 ## Preliminaries
 
 Before we begin, we need to cover some basic data types and helper methods.
-These utilities have already been implemented in the package object (in the file `package.scala`) for this
+These utilities have already been implemented in the package object (in the file `common.scala`) for this
 exercise.
 First, we will use the `RGBA` type to refer to the value of an image pixel.
 We will limit ourselves to 32-bit pixel depth images, so we define `RGBA` to