Explanation

To solve this problem, we need to find the rate at which the mason lays bricks, and then multiply that rate by the number of hours he works.

Rate = Number of bricks / Time = 280 bricks / 4 hours = 70 bricks per hour

If he works for 9 hours, he will lay:

70 bricks/hour x 9 hours = 630 bricks

So, the correct answer is: 630