A number is selected randomly from each of the given two sets.
Set 1: 1 , 2, 3, 4, 5, 7, 8
Set 2: 2, 3, 4, 5, 6, 7, 8, 9
The probability that the sum of the numbers is equal to 9 is:

A

$$\frac{14}{81}$$

B

$$\frac{8}{91}$$

C

$$\frac{7}{72}$$

D

$$\frac{7}{64}$$