BOSTON ( TheStreet) -- NightHawk Radiology ( NHWK) is one of several stocks trading on above-average volume Monday after the company was acquired in a $170 million deal.

NightHawk shareholders will receive $6.50 per share in cash from Virtual Radiologic, representing a 100% premium to the stock's closing price on Friday. The transaction is expected to be completed in the first quarter of 2011, the companies said.

Shares of NightHawk are surging by $3.14, or 96.5%, to $6.39. Volume topped 7.45 million shares, compared to the average daily share volume of 71,000.

Elsewhere, BioFuel Energy ( BIOF) shares are rallying by 63 cents, or 37.5%, to $2.31 after the company said Friday it has entered into a six-month $19.4 million bridge loan agreement with Greenlight Capital and an affiliate of Third Point LLC. The bridge loan was used to repay $17.9 million in working capital loans. Volume topped 2.49 million shares, compared to the average daily share volume of 218,000.

LDK Solar ( LDK) shares are jumping by $1.33, or 15%, to $10.18 after the company said it has borrowed $8.9 billion from the China Development Bank to fund its expansion efforts. Volume topped 12 million shares, compared to the average daily share volume of 2.97 million.

Shares of Rainmaker Systems ( RMKR) are spiking late in Monday's session, rising by 40 cents, or 37%, to $1.48 after the company said in a regulatory filing that it has entered into a statement of work under its vendor services agreement with Microsoft ( MSFT) to provide the company with global telesales and chat sales services.

Rainmaker said the statement of work covers the U.S., Europe and the Middle East, and Asia-Pacific regions and has an initial three-year term. Services are set to begin on Nov. 1, Rainmaker said. Volume topped 170,000 shares, compared to the average daily share volume of 9,000.

-- Written by Robert Holmes in Boston.

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