INSTRUMENT OF AMENDMENT TO THE
MDU RESOURCES GROUP, INC.
401(k) RETIREMENT PLAN

The MDU Resources Group, Inc. 401(k) Retirement Plan (as amended and restated
January 1, 2017) (the “K-Plan”), is hereby further amended, effective April 1,
2017, unless otherwise indicated, as follows:

1.
By adding the following new entry to Schedule B:

Knife River Midwest, LLC shall make supplemental contributions on behalf of its
Davis‑Bacon Employees in such amounts as may be necessary to satisfy the
Prevailing Wage Law’s required fringe cost to the extent that the sum of the
employer Matching and Profit Sharing Contributions, if any, for a period are
insufficient to satisfy the Prevailing Wage Law’s required fringe cost pursuant
to Supplement G.

Effective as of April 1, 2017.
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