The denominator here is 9, and the numerator is 24, respectively.
So, the number 2, 3, 4, 6, 8 and 12 has to be the numerator of the side length of the square because
2 × 12 = 24
3 × 8 = 24
4 × 6 = 24
By seeing the options, only 'a' has numerator as 6 and option 'b' has the numerator as 4.
Now, denominators can be 3 only, because:
3 × 3 = 9
So,
Only option 'a' matches both the denominator and the numerator.
63×43=249
So, the correct option is option 'a'.