<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def agerange(self, m, feh=0.0):
 """ For a given mass and feh, returns the min and max allowed ages. """

        ages = np.arange(self.minage, self.maxage, 0.01)
        rs = self.radius(m, ages, feh)
        w = np.where(np.isfinite(rs))[0]
        return ages[w[0]],ages[w[-1]]