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\sum\limits_{b=1}^4 (80b^6+4b^7 + 80(b+5)^6 + 4(b+5)^7) mod 100
\sum\limits_{b=1}^4 (80b^6+4b^7 + 80(b+5)^6 + 4(b+5)^7) mod 100
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