Harriet owns a piece of land in Yuen Long, upon which she intends to build a house made primarily of oak wood from Australia. She enters into a two-year contract with Freddy in early 2010, the Builder, to build the house for $3,000,000. Unfortunately, the price of the Australian oak wood increased significantly due to a bushfire which resulted in a shortage of the oak wood. Freddy requested an extra $70,500 to offset the extra expense. Harriet agrees and Freddy completed the work in 2012. However, Harriet refused to pay the extra $70,500. Advise Freddy as to whether he can get the extra payment.