A linear torsional spring deforms such that an applied couple moment M is related to the springs

Question:

A linear torsional spring deforms such that an applied couple moment M is related to the spring’s rotation u in radians by the equation M = (20 u) N # m. If such a spring is attached to the end of a pin-connected uniform 10-kg rod, determine the angle u for equilibrium. The spring is undeformed when θ = 0° .

A M = (20 0) N m