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diff --git a/2708/CH18/EX18.1/ex_18_1.sce b/2708/CH18/EX18.1/ex_18_1.sce
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+//Example 18.1 //Fermi Energy 
+clc;
+clear;
+//given data :
+P=.971D3;// density in Kg/m3
+N=6D26;// Avogadro number in atoms/Kg-mole
+W=22.99;//atomic weigh of sodium
+a=N*P/W;// electron density
+m=9.1D-31;// mass of electron in kg
+h=6.626D-34;// plank's constant in joules-sec
+E=((h^2)/(2*m))*(3*a/%pi)^(2/3);// fermi energy in J
+disp(E,"Fermi energy in J")
+//in book formula taken wrongly
diff --git a/2708/CH18/EX18.2/ex_18_2.sce b/2708/CH18/EX18.2/ex_18_2.sce
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+//Example 18.2 // Energy difference  
+clc;
+clear;
+//given data :
+h=1.0545D-34;// averge Plank's constant in J-s
+m=9.1D-31;// mass of electron in kg
+a=1D-10;// dimension of box in meter
+E1=((h^2)/(2*m))*(%pi/a)^2;//fermi energy of first level in j
+E2=2*((h^2)/(m))*(%pi/a)^2;//fermi energy of second level in J
+D=E2-E1;// difference of energy 
+disp(D,"energy difference in J")