Question 1: a crucial variable - how many working days per year - is missing. you can not multiply by 365
Questions 2: mark's income after tax is: (35000-4000)* (1-30%) + 4000 (tax free) = 25700. Initial saving is: 25700 * 20% = 5140; after 6 years: saving = 5140 * (1+10%)^6 = 9105 (choose C)