Amazon.com Inc. gave a weaker-than-expected forecast for operating profit in the current quarter, pointing toward a long list of factors including tariffs and trade that may cause consumers to pull back on spending.  The world’s largest online retailer projected operating profit of $13 billion to $17.5 billion, compared with an average estimate of $17.8 billion. Sales will be $159 billion to $164 billion in the period ending in June, the company said Thursday in a statement. Analysts, on average, expected $161.4 billion. Amazon shares have fallen about 13% this year as Wall Street weighs the impact of President Donald Trump’s tariffs on a retail operation that sources much of its goods from China.