54 The applicants submitted that even if they were not successful, or not substantially successful, in their challenges to the award so that the result reached by the arbitrator stood or stood without substantial variation, the arbitrator had also erred in law in determining that each party should be responsible for their or its own costs of the final arbitration but should each pay half the arbitration cost. It was submitted that this was such an erroneous exercise of the arbitrator's discretion with respect to costs that it revealed an error of law. However, the award for costs reflects the appreciation by the arbitrator that the builder had succeeded in the first interim award and in the final award and that the applicant owners had succeeded in the second and third interim awards so that the respective claims of the opposing parties, in effect, cancelled out. In my opinion, not only was this an acceptable exercise of discretion by the arbitrator but, so far as it is possible to assess, it is very likely to have been correct. After performing works to the value of $533,167.07 or a little less, having already been paid $434,000, the builder was ordered to pay damages of $76,992.40 producing a balance in favour of the builder of $22,174.67. On my findings, this balance should have been slightly less, namely $14,131.67, but the difference is only relatively small. Both the owners and the builder have had a measure of success in their claims and the balance between them in the end is small in proportion to the overall value of the works.