How many seconds are in 3.5 hours3.5 \text{ hours}3.5 hours?
12,600 s12,600 \text{ s}12,600 s
210 s210 \text{ s}210 s
3,500 s3,500 \text{ s}3,500 s
1,260 s1,260 \text{ s}1,260 s