P.M. BRIEFING : Bid for Prime Computer Extended

Minicomputer maker MAI Basic Four Inc. of Tustin said today that it has extended its hostile $1.2-billion tender offer for Prime Computer.

MAI Basic Four’s cash offer of $19.50 a share has been extended until midnight Monday.

Prime, based in Natick, Mass., has been fighting off MAI Basic Four’s offers for the last nine months. On June 23, it agreed to a $1.4-billion merger with DR Holdings Inc., a company organized by J. H. Whitney. The deal called for a $21.50-a-share cash tender offer for 79% of Prime, with shares not purchased converted into $22 principal in 15.5% senior subordinated debt due 2001.

MAI Basic Four, which had initially offered $20 a share, has said it will increase its bid but has not done so since the merger deal was announced.