Mahindra & Mahindra (M&M) has proposed an open offer to the existing shareholders of Punjab Tractors to buy up to 20% equity capital of the company, i.e 1, 21,51,140 shares, at Rs 360 per share.According to a release issued by M&M to the BSEE today, the specified date for the offer is March 12, 2007. The offer will open on May 3, 2007 and close on May 22, 2007.Also Read:Mahindra & Mahindra: Having a field dayPTL takeover spreads cheer among workersBadal govt orders probe into PTL dealM&M wins race for Punjab Tractors