Over the past year, a firm decreased its current assets and increased its current liabilities. as a result, the firm's net working capital:

As a result, the firm's net working capital: had to decrease

Net working capital is calculated by subtracting current liabilities to the current assets.

C. Assets - C Liability = Net working Capital

So, if the current assets is decreased and the current liability increased, it will cause a larger subtraction to the equation