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Use differential approximations in the following problem. A company will sell N units of a product after spending $x thousand in advertising, as given by N = 50x - x , 5s x$ 25. Approximately what increase in sales will result by increasing the advertising budget from $10,000 to $11,000? From $20,000 to $21,000? Find the differential dN. dN = ( ) dx The increase in sales from increasing the advertising budget from $10,000 to $11,000 is approximately units. (Type a whole number.) The increase in sales from increasing the advertising budget from $20,000 to $21,000 is approximately units. (Type a whole number.)