Need assistance on this word problem...

Singer I.M. Great publicly promised each of her fans an autographed photo of herself. The response was bigger than expected: all 220,000,000 people in the U.S. wrote for a picture(even her own brother). Calculate the number of hours I.M will need to sign all photographs, if she signs 1 picture every 3 seconds.

My answer was 11,000,000..please let me know if this is correct

1 picture in 3 seconds

220,000,000 pictures in 3(220,000,000) seconds

660,000,000 seconds
There are 3600 seconds in an hour, so divide by that.

(Drop the extra 2 zeroes on each number.)
6,600,000 / 36

It will take her 183,333.33 hours.