Which of following assumption is true about AJMM?

Modelling in AJMM is done with the following assumptions:
(i) Abrasives are spherical in shape and rigid. The particles are characterised by the mean grit diameter
(ii) The kinetic energy of the abrasives are fully utilized in removing material
(iii) Brittle materials are considered to fail due to brittle fracture and the fracture volume is considered to be hemispherical with diameter equal to chordal length of the indentation
(iv) For ductile material, removal volume is assumed to be equal to the indentation volume due to particulate impact.