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\ctrline {\bf CS154 ASSIGNMENT 5}
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\ctrline {Assigned Friday, April 29, due Friday, May 6}
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Do problems 4.1bd, 4.5a, and 4.19 from the book, in addition to the following:

I. Following the notation used in class, prove that ${X}↓{∞}$ is indeed
the minimum solution of $X = f(X)$.

II. Find the minimal solution to $X = rXr + s$, where $r$ and $s$ are
arbitrary regular expressions.

III.  Study for the midterm, which will be given on May 6.

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