I would say that all four answers are correct. Trade and commerce between civilizations really did help to exchange new ideas, spread languages, share new inventions, and make some people rich.
"Suppose an economist test the theory that when the price of leather increases, fewer pairs of shoes ..."His observations invalidate the testability of his hypothesis since they go against the ceteris paribus premise. This is further explained below.
<h3>What is an economist?</h3>
Generally, an economist is simply defined as a professional in economics.
In conclusion, To illustrate, "let's say an economist investigates the hypothesis that higher leather costs lead to fewer shoe purchases." Since his findings contradict the ceteris paribus premise, his hypothesis cannot be tested.
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B. The number of days’ sales in receivables is calculated as average accounts receivable divided by average daily sales