Rinku has just finished her first year of university. She wants to tour Europe when she graduates in three years. By having a part-time job through the school year and a summer job during the summer, she plans to make regular weekly deposits into a savings account, which bears 18 percent interest, compounded monthly. (a) If Rinku deposits $15 per week, how much will she save in three years? How about $20 per week? (b) Find out exactly how much Rinku needs to deposit every week if she wants save $5000 in three years. (4 points)