某中学为学生供应开水，用锅炉将200 ㎏的水从25 ℃加热到100 ℃，燃烧了6 ㎏的无烟煤。［无烟煤的热值是3.4 ×10⁷J/ ㎏］试求：

（1 ）锅炉内200 ㎏的水吸收的热量是多少焦耳？

（2 ）6 ㎏无烟煤完全燃烧放出的热量是多少焦耳？

（3 ）此锅炉的效率是多少？

Feasibility should be measured throughout the life cycle of system development. The scope and complexity of an apparently feasible project can change after the initial problems and opportunities are fully analyzed or after the system has been designed. Thus, a project that is feasible at one point may become infeasible later. The first feasibility analysis is conducted during the (1). The (2) represents a major feasibility analysis activity since it charts one of many possible implementations as the target for systems design. (3)  is a measure of how well the solution will work in the organization. It is also a measure of how people feel about the system. When it is determined in the later stages of the system life cycle, (4)  is often performed with a working prototype of the proposed system. This is a test of the system's user interfaces and is measured in how easy they are to learn and to use and how they support the desired productivity levels of the users. Economic feasibility has been defined as a cost-benefit analysis. The (5)  technique is a simple and popular method for determining if and when an investment will pay for itself.

空白（4）处应选择（）

A.performanc eanalysis

B.control analysis

C.usability analysis

D.interface analysis