Saatchi & Saatchi Co., the diversified British...

Saatchi & Saatchi Co., the diversified British advertising giant, said Friday that it agreed to acquire the influential computer research firm Gartner Group Inc. in a strategic expansion that builds its American consulting operations. Saatchi said it will pay $22.50 a share in cash, or $90.3 million, for Gartner, whose shares jumped $4.25 to $22 in NASDAQ over-the-counter trading. Saatchi said it will promptly start a tender offer to buy the Gartner shares. Shares remaining after the tender would be acquired in a merger at the same price.