A block of mass \(m\) is released from rest at the top of a ramp of length \(L\) inclined at an angle \(\theta\) above the horizontal. As the block slides down the ramp, a position-dependent retarding force of magnitude \(f(x) = bx\) acts on it, where \(x\) is the distance traveled along the incline from the top and \(b\) is a positive constant. What is the speed of the block when it reaches the bottom of the ramp?