Sarah aims to acquire, in 8 years, a special gadget priced today at 300 units in the local currency, with its cost rising by 6% annually due to market trends. To save for this, she plans to deposit 25 units into a savings account at the start of each of the initial 5 years. Additionally, she intends to contribute an unspecified amount, denoted as Y, at the end of the 3rd and 4th years to reach her goal. Her savings account offers a 12% annual equivalent rate. What is the value of Y needed to achieve her goal ?