Which of the following statements is incorrect regarding the fluid mosaic model of the plasma membrane?

(i) The plasma membrane is composed of a lipid bilayer of phospholipids.

(ii)Each phospholipid molecule has two ends, an outer head hydrophilic and an inner hydrophobic tail.

(iii) The protein molecules are arranged in two different ways:

(a) Peripheral proteins or extrinsic proteins

(b) Integral proteins or intrinsic proteins

(iv) The model was proposed by Robertson (1972).