Tech Mahindra won Satyam Bid

A number of reasons, some of which are: i) arbitrage discounts by available returns elsewhere until conversion, ii) perception that the deal might not meet regulatory approval or might fall through, iii) anticipation of price movements if it is stock for stock. The unusual situation would be the acquiree trading above the conversion price. Trading below is normal. As the conversion date draws near, the price will move very close to the conversion price. (I'm not following the Mahindra / Satayam acquisition.)

The thing to keep in the forefront is that the stock market anticipates the future (accurately or not). If the street thought "A" was going to buy "C" for $100, but "B" buys it for $50, the price of "C" may drop on disappointment. Sometimes stocks in a merger both go up, sometimes both go down, depending on the street's estimates of the resulting company. Usually, the acquiree will trade below the conversion price.

One would want to look at the specifics of the merger of Mahindra and Satayam, not just conversion price, but also financial statements and pro-forma earnings.

JUST TELL ME ONE THING IS IT NECESSARY THAT IT WILL TOUCH 58 ONE DAY OR THE ANOTHER

Excuse me, but I believe I answered that it depends on the specifics of the acquisition. I'm not familiar with the actual terms which should appear in the solicitation of shareholder votes (in most cases). If it is cash for shares, priced at 58, and it clears all regulatory approvals (government and shareholders), then the acquiror should pay 58 cash on the date stated. If it is priced in the acquiror's shares, the agreed upon number of shares should be delivered.