BISMARCK, N.D. (AP) — BISMARCK, N.D. (AP) — MDU Resources Group Inc. (MDU) on Thursday reported first-quarter earnings of $80.8 million. On a per-share basis, the Bismarck, North Dakota-based company said it had profit of 39 cents. The results missed Wall Street expectations. The average estimate of three analysts surveyed by Zacks Investment Research was for earnings of 42 cents per share. The energy, mining, construction and utilities company …