31. In every such case which is referred to the judge and assessors or to arbitrators for the purpose of determining whether any, and if so, what amount of compensation should be awarded, the judge and assessors or the arbitrators- (i) shall take into consideration- (a) the market value of the property or right injuriously affected at the time when the act was done or the work executed, (b) the damage sustained by the claimant by reason of such act or work injuriously affecting the property or right, (c) the consequent diminution of the market value of the property or right injuriously affected when the act was done or the work executed, and (d) whether any person has derived, or will derive, benefit from the act or work in respect of which the compensation is claimed or from any work connected therewith, in which case they shall set off the estimated value of such benefit, if any, against the compensation which would otherwise be decreed to such person; but (ii) shall not take into consideration- (a) the degree of urgency which has led to the act or work being done or executed, and (b) any damage sustained by the claimant, which if caused by a private person, would not in any suit instituted against such person justify a decree for damages.