Need help with the cope (Lagrange interpolation)

clc;
%a
x =[1 2 3 5 7 8];
fx =[3 6 19 99 291 444];
f1 = interp1(x,fx,2.8,'nearest');
f2 = interp1(x,fx,4.4,'nearest');
f3 = interp1(x,fx,7.1,'nearest');
fprintf("\nf(x) at x = 2.8: %d",f1)
fprintf("\nf(x) at x = 4.4: %d",f2)
fprintf("\nf(x) at x = 7.1: %d",f3)

%b 

x =[1 2 3 5 7 8];
fx =[ 3 6 19 99 291 444];
sum = 0;
a = 2;
for i = 1:length(x)
    u = 1;
    l = 1;
    for j = 1:length(x)
        if j ~= i
            u = u * (a - x(j));
            l = l * (x(i) - x(j));
        end
    end
    sum= sum + u / l * fx(i);
end
disp(sum);


sum = 0;
b = 3;
for i = 1:length(x)
    u = 1;
    l = 1;
    for j = 1:length(x)
        if j ~= i
            u = u * (b - x(j));
            l = l * (x(i) - x(j));
        end
    end
    sum= sum + u / l * fx(i);
end
disp(sum);

c = 4;
for i = 1:length(x)
    u = 1;
    l = 1;
    for j = 1:length(x)
        if j ~= i
            u = u * (c - x(j));
            l = l * (x(i) - x(j));
        end
    end
    sum= sum + u / l * fx(i);
end
disp(sum);

%c

x = [ 2.8, 4.4 ,7.1];
fx = [19, 99, 291];

sum = 0;
a = 2;
for i = 1:length(x)
    u = 1;
    l = 1;
    for j = 1:length(x)
        if j ~= i
            u = u * (a - x(j));
            l = l * (x(i) - x(j));
        end
    end
    sum= sum + u / l * fx(i);
end
disp(sum);


sum = 0;
b = 3;
for i = 1:length(x)
    u = 1;
    l = 1;
    for j = 1:length(x)
        if j ~= i
            u = u * (b - x(j));
            l = l * (x(i) - x(j));
        end
    end
    sum= sum + u / l * fx(i);
end
disp(sum);

c = 4;
for i = 1:length(x)
    u = 1;
    l = 1;
    for j = 1:length(x)
        if j ~= i
            u = u * (c - x(j));
            l = l * (x(i) - x(j));
        end
    end
    sum= sum + u / l * fx(i);
end
disp(sum);

I need to double check that AM I doing it right?

You are given the following errorless dataset:x= [1 2 3 5 7 8]

f(x) = [3 6 19 99 291 444 ]

a.Use nearest neighbour interpolation to find f(x) for the following x values: 2.8, 4.4, and 7.1

b.Implement a MATLABfunctionor scriptto perform interpolation based on the closest 2, 3, and 4 points using Lagrangian interpolating polynomials

c.Run your function/scripton the x values given in a)for the closest 2-, 3-, and 4-point Lagrangian interpolating polynomia