7. Roslyn purchased a RM4,000 computer. She has to pay RM2,000 down payment and 20 weekly payments of RM1 10 each. Find the approximate effective rate that was charged by using the constant ratio formula. 8. An electric stove is selling for RM1,800 cash. A cash purchase is entitled to a 10% discount. Through the instalment plan, the stove can be purchased for RM600 down payment and RM100 a week for 12 weeks. Find the approximate effective rate charged to the instalment buyer by using the constant ratio formula