Que: Determine the set of all integers a such that a ≡ 3 (mod 7) such that −21 ≤ x ≤ 21.

a. {−21, −18, −11, −4, 3, 10, 16}

b. {−21, −18, −11, −4, 3, 10, 17, 24}

c. {−24, -19, -15, 5, 0, 6, 10}