In checking the petty cash, a clerk counts $q$ quarters, $d$ dimes, $n$ nickels, and $c$ cents. Later, he discovers that $x$ of the nickels were counted as quarters and $x$ of the dimes were counted as cents. To correct the total obtained, by how many cents must the clerk adjust the total? The original answer is in the form $kx$, please give the value of $k$.

Let's think step by step and output the final answer within \boxed{}.
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