Please help with regards to property law.

(b) Brad is a builder and developer. In the last few years, his business has been booming due to the high demand for housing and he desperately needed more carpenters. He persuaded his older son Zack to train as a carpenter instead of going to university. His younger son Roy went to university and graduated with a degree of civil engineering. He pursued a career in an engineering consulting firm. In his role as a carpenter, Zack made significant contributions to Brad's building business. Brad promised him that 'one day the building business will be yours'. Brad and his wife Angie separated last year and their assets were split between them as a consequence. Angie received half of their assets, estimated to be worth $1.5 million while Brad received the house and the building business. Sadly, last month Brad died from a workplace accident. In his will, he left his house (worth about $300,000) to Zack and the rest of his estate including the building business (estimated to be worth $1.2 million) to his younger son Roy. Zack is unhappy with what he is given under Brad's will. The housing market has now slowed down and Zack, who has no other qualification or skill, is finding it hard to earn enough income to provide for basic needs. Zack has two school-aged children. His wife is not working due to health problems. OUTLINE, with reference to relevant legislations and case law, the options available to Zack to challenge Brad's will in respect of his entitlements to Brad's estate. There is no issue with the validity of the will. Do not discuss contract or trust law in your answer. (15 Marks) TOTAL: 25 MARKS