If I send a code $,$ can u please check if that is right?

$\%$ Parameters

L $=1$; $\%$ Reactor length

N $=100$; $\%$ Number of grid points

D $=0\mathrm{.}1$; $\%$ Diffusion coefficient

gamma $=0\mathrm{.}02$; $\%$ Reaction rate for A

delta $=0\mathrm{.}05$; $\%$ Reaction rate for B

zeta $=0\mathrm{.}0$; $\%$ Reaction rate for U

beta $=1\mathrm{.}5$; $\%$ Boundary condition for B at x$=0$

epsilon $=0\mathrm{.}1$; $\%$ Boundary condition for A at x$=$L

eta $=0\mathrm{.}05$; $\%$ Boundary condition for B at x$=$L

theta $=0\mathrm{.}1$; $\%$ Boundary condition for U at x$=$L

$\%$ Grid setup

dx $=$ L $/($N $-1)$;

x $=$ linspace$(0,$ L$,$ N$)$;

$\%$ Initial concentration guesses

yA $=$ ones$(1,$ N$)$;

yB $=$ ones$(1,$ N$)$;

yU $=$ zeros$(1,$ N$)$;

$\%$ Boundary conditions at x $=0$

yA$(1)=1$;

yB$(1)=$ beta $+0\mathrm{.}5$;

yU$(1)=0$;

$\%$ Boundary conditions at x $=1$

yA$($N$)=$ epsilon;

yB$($N$)=$ eta;

yU$($N$)=$ theta;

$\%$ Finite difference matrix for second derivative $($central difference$)$

A $=$ diag$(-2*$ones$(1,$ N$-2))+$ diag$($ones$(1,$ N$-3),1)+$ diag$($ones$(1,$ N$-3),-1)$;

A $=$ D $*$ A $/$ dx$^2$;

$\%$ Initializing the old values for convergence check

yA$\_$old $=$ yA$(2$:N$-1)$;

yB$\_$old $=$ yB$(2$:N$-1)$;

yU$\_$old $=$ yU$(2$:N$-1)$;

$\%$ Iteratively solve for steady$-$state concentrations

tolerance $=1$e$-6$;

max$\_$iter $=5000$;

for iter $=1$:max$\_$iter

$\%$ Reaction terms for each species

R$\_$A $=-$yA$(2$:N$-1)-$ gamma $*$ yA$(2$:N$-1)$;

R$\_$B $=-2*$ yA$(2$:N$-1)-$ delta $*$ yB$(2$:N$-1)+$ zeta $*$ yU$(2$:N$-1)$;

R$\_$U $=$ delta $*$ yB$(2$:N$-1)-$ zeta $*$ yU$(2$:N$-1)$;

$\%$ Update concentration profiles

yA$(2$:N$-1)=$ A $\backslash$ R$\_$A$\text{'}$;

yB$(2$:N$-1)=$ A $\backslash$ R$\_$B$\text{'}$;

yU$(2$:N$-1)=$ A $\backslash$ R$\_$U$\text{'}$;

$\%$ Enforce boundary conditions directly

yA$(1)=1$; $\%$ Boundary condition for yA at x$=0$

yB$(1)=$ beta $+0\mathrm{.}5$; $\%$ Boundary condition for yB at x$=0$

yU$(1)=0$; $\%$ Boundary condition for yU at x$=0$

yA$($N$)=$ epsilon; $\%$ Boundary condition for yA at x$=1$

yB$($N$)=$ eta; $\%$ Boundary condition for yB at x$=1$

yU$($N$)=$ theta; $\%$ Boundary condition for yU at x$=1$

$\%$ Check for convergence $($steady state$)$

if max$($abs$([$yA$(2$:N$-1)-$ yA$\_$old, yB$(2$:N$-1)-$ yB$\_$old, yU$(2$:N$-1)-$ yU$\_$old$]))<$ tolerance

break;

end

$\%$ Save the old concentrations for next iteration

yA$\_$old $=$ yA$(2$:N$-1)$;

yB$\_$old $=$ yB$(2$:N$-1)$;

yU$\_$old $=$ yU$(2$:N$-1)$;

end

$\%$ Plot the concentration profiles

figure;

plot$($x$,$ yA$,\text{'}$r$-\text{'},$ x$,$ yB$,\text{'}$g$-\text{'},$ x$,$ yU$,\text{'}$b$-\text{'},$ 'LineWidth', $2)$;

title$(\text{'}$Steady$-$State Concentration Profiles'$)$;

legend$(\text{'}$yA$\text{'},\text{'}$yB$\text{'},\text{'}$yU$\text{'})$;

xlabel$(\text{'}$Position $($x$)\text{'})$;

ylabel$(\text{'}$Concentration$\text{'})$;

grid on;