In Marx's view, what is the difference between labor and surplus labor

1.In Marx's view, what is the difference between labor and "surplus" labor? How is the capitalist able to extract surplus labor?

2.Why did Marx believe that capitalism would fall on its own?  Why did his predictions not come true? (hint: how has the economy changed since Marx’s time?

3.Economists regard the labor market as a negation between buyers and sellers of labor,  Does this describe what happened at Carnegie’s Steel Mill?  How Did Herbert Spencer’s “Social Darwinism” influence Carnegie’s thinking?

4.Economists regard an ideal “free market” as not subject to the control of anyone.  Considering his handling of the railroads and his buyout of Carnegie Steel, Would J. P. Morgan have agreed?