A projectile is launched from ground level with an initial velocity of 60 m/s at an angle $\theta$ above the horizontal. The range formula is $R = \frac{v_0^2 \sin(2\theta)}{g}$, where $g = 10$ m/s². If the projectile must clear a 15-meter-high wall located 180 meters away, what is the minimum launch angle (to the nearest degree) required?