Autodesk Inc, San Rafael, California was not prepared to be gazumped on its agreed bid for Softdesk Inc, and it has raised its offer to $15 a share, or about $90m, after a second, unidentified, suitor made a competing proposal. Under the definitive agreement, Autodesk will pay the $15 a share in new shares based on the average closing prices for the five trading days before the closing date. The originally agreed price had been $12 a share, or about $72m. Dave Arnold, chief executive of Softdesk, said the Henniker, New Hampshire company was committed to the Autodesk merger.