Triangle With Squares!

Geometry Level 4

Given a triangle $ABC$ , construct two squares $ABPQ$ and $ACRS$ . Suppose that $M$ is the midpoint of $PR$ . Join $MB$ and $MC$ . Find $\angle BMC$ .

Details and Assumptions:

$P$ and $C$ are on opposite side of $AB$ .
$R$ and $B$ are on opposite side of $AC$ .

Triangle With Squares!

If you're interested, here is follow up question.