Linear Transformations · Challenge problem

Let $R_x$ be the rotation of $\mathbb{R}^3$ by $90^\circ$ about the $x$-axis and $R_y$ the rotation by $90^\circ$ about the $y$-axis, each counterclockwise when viewed from the positive end of its axis looking toward the origin. The composite $R_y\circ R_x$ (apply $R_x$ first) is a rotation about some axis through the origin. Through how many degrees does it rotate? (Give an angle in $[0, 180]$.)