Solve the open sentence.
–2 ≤ n + 4 ≤ 7

a.n ≥ 6 and n ≤ –4

b.n ≤ 2 and n ≤ 7

c.n ≤ –6 and n ≤ 4

d. n ≥ –6 and n ≤ 3