A block of mass \(m\) rests on a flat horizontal surface. Starting at time \(t = 0\), a constant horizontal force of magnitude \(F_0\) is applied to the block. The coefficient of static friction between the block and the surface decreases over time according to \(\mu_s(t) = \mu_0 - bt\), where \(\mu_0\) and \(b\) are positive constants, and \(F_0 < \mu_0 mg\). In terms of \(m\), \(g\), \(F_0\), \(\mu_0\), and \(b\), at what time \(t\) does the block begin to slip?