(a) To estimate the amount Dennis gets paid in a week, you can multiply his hourly wage by the number of hours he works: £8.79 * 39 hours = £342.81 (rounded to the nearest penny).
(b) This estimate is slightly over the actual amount Dennis gets paid because it doesn't account for any additional earnings from overtime, bonuses, or deductions like taxes. However, it's a reasonably close estimate for a regular workweek without those factors.