Solution:
The following will be used:
clc% clears screen
clear all% clears history
close all% closes all files
format long
MY CURVEFIT(7)
function y = MYCURVEFIT(x)
X = 0:0.5:20;
Y = [14, 16, 18, 22, 28, 35, 50, 68, 90, 117, 154, 200, 248, 309, 378, 455, 550, 654, 770, 900, 1044, 1200, 1378, 1560, 1778, 2004, 2250, 2500, 2800, 3100, 3434, 3786, 4158, 4555, 4978, 5424, 5900, 6401, 6930, 7474, 8074];
C = polyfit (X,Y,3);
y = polyval (C,x);
end