1. **Stating the problem:** William earns 148 kr per hour and works between 25 and 28 hours per month for a year. We need to determine if his annual income exceeds 100000 kr, which means he must pay tax and thus needs a skattekort (tax card). Otherwise, he can have a frikort (tax exemption card). 2. **Formula and rules:** Annual income is calculated as $$\text{Income} = \text{hourly wage} \times \text{hours per month} \times \text{months per year}$$ 3. **Calculate minimum annual income:** $$148 \times 25 \times 12 = 148 \times 300 = 44400$$ 4. **Calculate maximum annual income:** $$148 \times 28 \times 12 = 148 \times 336 = 49728$$ 5. **Interpretation:** William's annual income ranges from 44400 kr to 49728 kr, both below the 100000 kr threshold. 6. **Conclusion:** Since William's income is less than 100000 kr, he does not need to pay tax and can have a frikort.