If the wealthiest 10% of the country paid the equivalent of an additional $3.70 per hour in tax, we'd have an extra $20 billion per year for health, education, housing, climate change, etc (10% of 5.2M) × $3.70 × 40 × 5 × 52 > $20B

I get 40 hours and 52 weeks, but what does the 5 represent?