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Imagine a worker who is hired for an hour and paid $10. Once in the capitalist’s employ, the capitalist can have him operate a boot-making machine using which the worker produces $10 worth of work every fifteen minutes. Every hour, the capitalist receives $40 worth of work and only pays the worker $10, capturing the remaining $30 which, after deduction of costs (the leather, depreciation of the machine, etc.) leaves a residual, i.e. surplus value or profit.
