We are given a set of n countries that are engaged in trade with one another. For each country i, we have the value si of its budget surplus; this number may be positive or negative, with a negative number indicating a deficit. For each pair of countries i, j, we have the total value eij of all exports from i to j; this number is always nonnegative. We say that a subset S of the countries is free-standing if the sum of the budget surpluses of the countries in S, minus the total value of all exports from countries in S to countries not in S, is nonnegative. Give a polynomial-time algorithm that takes this data for a set of n countries and decides whether it contains a nonempty free-standing subset that is not equal to the full set.

Which process would best represent the opposite of exhausting air from a system?

Acomputer is a multipurpose device that accepts input, processes data, stores data, and produces output, all according to a series of stored . the processing unit of most modern computers is a(n) . the instructions that tell a computer how to carry out a task are referred to as computer , which are distributed as software. computers run three main types of software: software, system software, and development tools. an example of system software is a computer system, which is essentially the master controller for all the activities that a digital device performs. digital devices are constructed using tiny electronic components that represent data bits as electrical signals. the system unit houses the system board, which contains several circuits made from semiconducting materials. computers come in three popular form factors: component, , and slate. many of today's digital devices operate on battery power supplied by ion batteries. battery life and lifespan can be extended by following good battery management practices.

How should you specify box sizes on a web page if you want the boxes to vary according to the font size of the text they contain? a. in pixels b. in inches c. as percentages d. in em units