Please answer all these subquestions in detailed steps! For each of the following transactions, find the contribution to the current year's GDP. Explain the effects on the product, income and expenditure accounts.

1. On Jan 1, you purchase 10 notebooks at a price of $5 each. The seller produced the notebooks the previous year, and held them as inventories.
2. Someone purchases a 1921 Westmount mansion for $5,000,000. The broker's fee is 4%.
3. A new mother enters the workforce, taking a job as a baker that will pay $30,000 over the year. The mother must pay $4,000 a year for professional child-care services.
4. A car rental agency updates it fleet: it buys $100,000,000 worth of new cars from a domestic producer. It sells its old fleet to a used car dealer for $40,000,000. The dealer resells the cars to the public for $60,000,000.