def METHOD_NAME():
    with DimensionalAnalysis():
        # Arrange
        si = constants_defaults.si
        formulae = Formulae()
        sut = formulae.hygroscopicity.r_cr
        kp = 0.5
        rd = 0.1 * si.micrometre
        T = 300 * si.kelvins
        sgm = constants_defaults.sgm_w
        # Act
        r_cr = sut(kp, rd**3, T, sgm)
        # Assert
        assert r_cr.to_base_units().units == si.metres