How equation 4 generate by substituting equation 1 and equation 2 in equation 3. Show me the details work please

When the concentration of the transferring ion in the aqueous phase is in excess relative to the ionophore in the organic phase, the observed current for facilitated ion transfer is equal to the rate of departure of the complesed ion. In the case of spherical diffusion this reads as ,_ 2,510,, I _ r , 2 FAD. (cs-cw * ,- *'(o.ct:.) a) where the subscripts C and Cl refer to the ionophore and complexed ion. respectively, the superscripts b and (I refer to bulk and surface concentrations and where F is the Faraday constant, B the diffusion coefcient, A the area of the microITIES and r the radius of the tip of the pipette. The observed limiting current for the case where the initial concentration of the complexed ion is zero in the organic phase is given by , 2 FA . z FAD. 4'u = 1 BL (3'3, = I u Ciro (2) r r Also, the kinetic expression for the current is i: ziFA(EappC:I_EappC:I) (3') where 1:.\" and it\