clc
r1=0.05; //m
r2=0.1; //m
r3=0.15; //m
T1=1000; //K
T3=500; //K
e1=0.05;
e2=e1;
e3=e1;
a=5.67*10^(-8);

F_12=1;
F_23=1;

// A1*a*(T1^4-T2^4)/(((1-e1)/e1) + 1/F_12 + ((1-e2)/e2)*A1/A2) = A2*a*(T2^4-T3^4)/(((1-e2)/e2) + 1/F_23 + ((1-e3)/e3)*A2/A3)

// A1/A2=r1/r2=5/10=0.5
// A2/A3=r2/r3=10/15=0.67

//Solving this we get 
T2=770; //K

Q1=a*(T1^4-T2^4)/(((1-e1)/e1) + 1/F_12 + ((1-e2)/e2)*r1/r2);
disp("Heat flow per m2 area of cylinder 1 =")
disp(Q1)
disp("W")