WASHINGTON (Reuters) -A lawyer for the U.S. Justice Department pressed a Google executive on Wednesday about techniques the search and advertising giant used to push up online advertising prices in an allegedly unfair way. Testifying at a once-in-a-generation antitrust trial in Washington where the United States has accused Google of abusing its dominance of search and some advertising, Google executive Adam Juda said the company uses a formula, which includes the quality of an ad, to decide who wins auctions that are used to place advertising on websites. The Justice Department has accused Google of manipulating online auctions - a multibillion dollar industry dominated by Google - with these formulas to favor its own bottom line.