What is the fine-grained topic of the following text: Lend Lease announced that it would commence the final and tallest of the 3 commercial towers at Barangaroo South, and that Pricewaterhouse Coopers Australia and HSBC Bank Australia have signed leasing arrangements for the 49 storey tower. Only return the topic.
Commencement of the final commercial tower at Barangaroo South by Lend Lease and its leasing arrangements.