(a) How does working capital differ from real capital investments? (b) Identify a principle that firms can efficiently use to determine whether or not it is profitable to hold a specific current asset or current liability, and describe how to use it? (c) Why do firms managers usually have to spend a disproportionate amount of time managing their working capital? (d) Describe a working capital management technique that firms use to reduce their illiquidity risk, default risk, or interest rate risk. (e) Identify a financial ratio that can help financial managers identify a working capital management problem, and explain how it can do this.