The review by the board of a decision of the department shall be limited to the questions:

1. (a) Whether the department has proceeded without, or in excess of, its jurisdiction.
2. (b) Whether the department has proceeded in the manner required by law.
3. (c) Whether the decision is supported by the findings.
4. (d) Whether the findings are supported by substantial evidence in the light of the whole record.
5. (e) Whether there is relevant evidence, which, in the exercise of reasonable diligence, could not have been produced or which was improperly excluded at the hearing before the department.