The Board shall decide each appeal within a reasonable time, and notice thereof shall be given to all parties in interest. The decision of the Board shall be immediately filed in its office, and if a variance is granted, it must be entered in the minutes of the Council so as to be of public record. In the exercise of its functions upon such appeals or upon exceptions, the Board may, in conformity with law, reverse or affirm, wholly or partly, or modify the order, requirement, decision or determination appealed from or make such order, requirement, decision or determination as, in its opinion, ought to be made. The Board must reach a decision within 45 days or it will be deemed a favorable decision.