Lars, divorced, works as a pilot, earning 3,500 net monthly (his salary is always paid at the end of the month). He saves 1,000 monthly at the end of each month. On January 1, 2020, he will have 40,000 in his savings account. However, he becomes technically unemployed for three months at the beginning of March 2020, which means that he only earns 1,500 per month in March, April and May. As a result, he will be obliged to take 750 from his savings account in those months. After these three months, he can resume his work and earn again 3,500 per month. How much is in his savings account at the end of June 2020 if the savings account generates an annual effective interest rate of 0.11%?

However, Lars' ex, Veronique, is not satisfied that he doesn't pay alimony in those 3 months. Normally she gets 800 from him every month. He agrees with her that he will replace the 800 of March and the 800 of April by paying an extra amount for 4 trimesters. The first time he will pay at the end of June 2020. How much extra will he have to pay her each trimester if the semestrial interest rate is 1.8%?

Lars finds it too difficult to pay 800 each month and decides to replace all payments of the year 2020 from March to December (so 10 payments) by one single payment of 8,000. When should he pay this 8,000 to Veronique if the effective monthly interest rate is 0.1%?