3 (a) Mariam works in a shop. She earns $5.20 per hour. She also earns a bonus of 15% of the value of the items she sells in a week. (i) In one week she works for 32 hours and sells items with a value of £2450. Calculate Mariam’s total earnings for the week. (ii) In another week, Mariam worked for 28 hours and earned a total of $409.60 . Calculate the value of the items she sold that week (b) (i) Jack opens a bank account paying simple interest. He pays in $800 and leaves it in the account for 4 years. At the end of 4 years he closes the account and receives $920. Calculate the percentage rate of simple interest paid per year. (ii) Jack uses some of the $920 to pay for a holiday and a computer. He saves the remainder. The money is divided between the holiday, computer and savings in the ratio 4 : 5 : 7 . Calculate the amount he saves.