t = [0, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120];
y = [4.99, 4.05, 3.31, 2.69, 2.19, 1.78, 1.45, 1.15, 0.96, 0.79, 0.65, 0.53, 0.44];

calcy = (5*exp(-x/36));
error = abs(calcy - y);

hold on

plot(t,calcy)
plot(t,y)
plot(t,error)