In municipal water supply design, the fire demand of a city may be estimated using several empirical formulas; identify the correct statement about available methods.

Introduction / Context:
Fire demand is the short-duration, high-flow requirement that a water distribution system must be able to supply during firefighting events. Designers estimate this demand using empirical formulas derived from historical data and urban characteristics. Knowing which formulas exist and when they apply is essential for sizing mains, hydrants, storage, and pumps.

Given Data / Assumptions:

• We are comparing named empirical methods: Kuichling's, Freeman, Underwriters (often called National Board of Fire Underwriters), and Buston/Bustan.
• Question asks which of these are used to work out city fire demand.
• No numerical inputs are provided; this is a recognition/recall item.

Concept / Approach:
Multiple empirical formulae are cited in standard water-supply texts for Indian and international practice. Each provides an estimated peak flow based on population or service area. The key idea is that different cities and codes may prefer different correlations, but all listed formulas are legitimate approaches to compute fire demand.

Step-by-Step Solution:
Step 1: Recall that fire demand estimation is not unique; several time-tested formulae exist.Step 2: Recognize the names Kuichling, Freeman, Underwriters, and Bustan as standard in design literature.Step 3: Conclude that all listed methods can be used to work out fire demand.

Verification / Alternative check:
Cross-comparing results from two or more formulas for the same population often yields values within a reasonable range. Designers then select the governing (usually higher) value considering local fire codes and risk assessments.

Why Other Options Are Wrong:
Kuichling's formula only: Incomplete—there are other accepted formulas.Freeman formula only: Incomplete for the same reason.Under Writers formula only: Also incomplete.Bustan's formula only: Again, not comprehensive.

Common Pitfalls:

• Using a single formula universally without checking local standards or insurance underwriters’ requirements.
• Ignoring peak-hour plus fire-flow scenarios; storage and main sizes should consider concurrent demands.
• Not validating available residual pressure at hydrants while meeting calculated flow.

Final Answer:
All the above.