3. $\mathrm{ABCD}$ is a trapezoid with bases $\mathrm{AD}=6$ and $\mathrm{BC}=10$. It turns out that the midpoints of all four sides of the trapezoid lie on the same circle. Find its radius.

If there are multiple correct answers, list them in any order separated by a semicolon.
Answer: 4.

## Examples of answer notation:

45

$4 ; 5$

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