* Abbot to buy Solvay's drugs unit for $6.6 billion
* Xerox will acquire ACS in a $6.4 billion deal
* Apple's iPhone to go on sale in China in October (Adds details, changes quote)
By Rodrigo Campos
NEW YORK, Sept 28 (Reuters) - U.S. stocks were set for a higher open Monday as more merger and acquisition activity and the last days of the third quarter encouraged investors following three sessions of losses.
Xerox Corp will buy Affiliated Computer Services Inc for $6.4 billion in a cash and stock deal that expands the copier company into technology outsourcing and data management.
Xerox shares fell 9.4 percent to $8.17 in premarket trade while ACS shot up 21 percent to $57.27.
Abbott Laboratories said it would buy the drugs unit of Solvay in a $6.6 billion deal, giving Abbott full control of its Belgian development partner's cholesterol treatments and exposure to emerging markets.
Abbott stock rose 2 percent.
"It is a good sign that there is (merger and acquisition) activity because evidently there is funding and liquidity," said Tom Alexander, head of Alexander Trading in Savannah, Georgia.
"Companies interested in buying companies has traditionally been a sign of optimism in the market."
A Jewish holiday observed Monday and the end of the third quarter two days later could translate into thin volume and volatility as fund managers reposition their assets, Alexander said.
S&P 500 futures rose 6.3 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures gained 42 points and Nasdaq 100 futures added 9 points.
The Dutch biotechnology firm Crucell said Johnson & Johnson bought 14.6 million new Crucell shares for over $400 million as part of a flu vaccine development deal.
GenTek Inc shares soared 40 percent after the maker of specialty chemicals and vehicle engine components said it agreed to a takeover by a subsidiary of private equity firm American Securities LLC for $411 million in cash.
China Unicom, that country's No. 2 mobile carrier, said Apple Inc's popular iPhone would be sold in China starting in October at a retail price of about $730.. France Telecom's Orange also said it would sell iPhones later this year.
Apple shares edged 1.3 percent higher before the open.
The Federal Reserve Bank of Chicago said its National Activity Index was minus 0.90 in August, down from a revised minus 0.56 in July, but its three-month moving average of economic indicators improved for the seventh straight month to its highest level since June 2008.
U.S. stocks fell for a third straight day Friday on disappointing housing and durable goods data, while Research In Motion's Inc's lackluster results dented optimism about technology spending.