Probability-1

Probability Level 5

Tiles in a bag are numbered from $\left\{ 0,1,2,3,4,\ldots,98,99 \right\}.$ Two tiles with the numbers $a$ and $b$ are randomly drawn from the bag with replacement. What is the probability that the number $3^a+7^b$ has a digit equal to $8$ at the unit place?

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