"Based on economic theory, what do you predict would be the value of the marginal product of labor at the highest possible level of production?"

Explanation: The Marginal Product of Labour reaches it maximum value at the point of diminishing returns and then after this point the marginal product of labour begins to fall.

The law of diminishing returns states that as a units of one input are added while all other inputs are held constant, a point will be reached where the resulting additions to output will begin to decrease; that is at this point marginal product will start declining.

Going further at the point of diminishing returns, the marginal product of labour is still above the average product of labour and the average product of labour will continue to increase until marginal product of labour equals average product of labour.