Help with initial approximation of parameters [X Y Z] for intersection by linear method

See BOLDED below (lines 68-70). I'm stumped on those three lines in this "fill in the code" assignment. Thank you for any gudiance!

clc;

clear all;

f0_mm=3.61; %mm

f0_px=3.61/6.16*4000; %pixel

data=readmatrix('intersection_pt.txt');

focal=f0_px; % update

W=4000;

H=3000;

pt_id=data(:,1);

x1=data(:,2)-W/2;

y1=H/2-data(:,3);

x2=data(:,4)-W/2;

y2=H/2-data(:,5);

[m,n]=size(data);

EO1= %%% You can find the EO information from the Lab slide

EO2= %%%

XL1=EO1(1,1);

YL1=EO1(2,1);

ZL1=EO1(3,1);

o1=EO1(4,1);

p1=EO1(5,1);

k1=EO1(6,1);

XL2=EO2(1,1);

YL2=EO2(2,1);

ZL2=EO2(3,1);

o2=EO2(4,1);

p2=EO2(5,1);

k2=EO2(6,1);

M1=[cos(p1)*cos(k1) cos(o1)*sin(k1)+sin(o1)*sin(p1)*cos(k1) sin(o1)*sin(k1)-cos(o1)*sin(p1)*cos(k1);

-cos(p1)*sin(k1) cos(o1)*cos(k1)-sin(o1)*sin(p1)*sin(k1) sin(o1)*cos(k1)+cos(o1)*sin(p1)*sin(k1);

sin(p1) -sin(o1)*cos(p1) cos(o1)*cos(p1)];

M2=[cos(p2)*cos(k2) cos(o2)*sin(k2)+sin(o2)*sin(p2)*cos(k2) sin(o2)*sin(k2)-cos(o2)*sin(p2)*cos(k2);

-cos(p2)*sin(k2) cos(o2)*cos(k2)-sin(o2)*sin(p2)*sin(k2) sin(o2)*cos(k2)+cos(o2)*sin(p2)*sin(k2);

sin(p2) -sin(o2)*cos(p2) cos(o2)*cos(p2)];

X_init=zeros(m,1);

Y_init=zeros(m,1);

Z_init=zeros(m,1);

result=zeros(m,3);

for i=1:m

u1=M1(1,1)*x1(i,1)+M1(2,1)*y1(i,1)+M1(3,1)*-focal;

v1=M1(1,2)*x1(i,1)+M1(2,2)*y1(i,1)+M1(3,2)*-focal;

w1=M1(1,3)*x1(i,1)+M1(2,3)*y1(i,1)+M1(3,3)*-focal;

C1=%%% You can find the equations for intersecction from the Lab slide

C2=%%%

u2=M2(1,1)*x2(i,1)+M2(2,1)*y2(i,1)+M2(3,1)*-focal;

v2=M2(1,2)*x2(i,1)+M2(2,2)*y2(i,1)+M2(3,2)*-focal;

w2=M2(1,3)*x2(i,1)+M2(2,3)*y2(i,1)+M2(3,3)*-focal;

C3=%%%

C4=%%%

B=%%%

f=%%%

W=eye(4,4);

N=B'*W*B;

t=B'*W*f;

del=inv(N)*t;

X0=%%% initial approximation of X, Y, Z are the elements of del.

Y0=%%%

Z0=%%%

L=[x1(i,1);y1(i,1);x2(i,1);y2(i,1)];

L0=L;

par_0=[X0;Y0;Z0];

keep_going=1;

last_phi=10;

iter=0;

while keep_going==1

syms xx1 yy1 xx2 yy2 X Y Z

U1=M1(1,1)*xx1+M1(2,1)*yy1+M1(3,1)*-focal;

V1=M1(1,2)*xx1+M1(2,2)*yy1+M1(3,2)*-focal;

W1=M1(1,3)*xx1+M1(2,3)*yy1+M1(3,3)*-focal;

U2=M2(1,1)*xx2+M2(2,1)*yy2+M2(3,1)*-focal;

V2=M2(1,2)*xx2+M2(2,2)*yy2+M2(3,2)*-focal;

W2=M2(1,3)*xx2+M2(2,3)*yy2+M2(3,3)*-focal;

FF=[(X-XL1)-(Z-ZL1)*U1/W1;

(Y-YL1)-(Z-ZL1)*V1/W1;

(X-XL2)-(Z-ZL2)*U2/W2;

(Y-YL2)-(Z-ZL2)*V2/W2];

BB=%%% use jacobian() function

AA=%%% use jacobian() function

X=par_0(1,1);

Y=par_0(2,1);

Z=par_0(3,1);

xx1=L0(1,1);

yy1=L0(2,1);

xx2=L0(3,1);

yy2=L0(4,1);

F=%%% evaluate FF using eval() function

B=%%% evaluate BB using eval() function

A=%%% evaluate AA using eval() function

Q=inv(W);

Qe=A*Q*A';

We=inv(Qe);

f=%

N=%

t=%

delta=%

v=%

phi=v'*W*v;

obj=abs((last_phi-phi)/last_phi)

if (obj<0.0001)

keep_going=0

disp('we have converged');

end

L0=L+v;

par_0=par_0+delta;

if (obj<0.0001)

result(i,:)=par_0;

end

if (iter>100)

keep_going=0;

disp('too many iterations');

end

last_phi=phi;

iter=iter+1;

end

end