What is the easiest way to solve this?

If a + b = 9, what is the value of ab?

(1) a - b = 5

(2) b - a = -5


Statement (1) ALONE is sufficient, but statement (2) alone is insufficient.

Statement (2) ALONE is sufficient, but statement (1) is insufficient.

BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.

EACH statement ALONE is sufficient.

Statements (1) and (2) TOGETHER are NOT sufficient.

Ans D