find the domain, period, range, and amplitude of the cosine function.

y = -6 cos 4x

a. domain = -1/2 ≤ x ≤ 1/2; period = 6; range: - -6 ≤ y ≤ 6; amplitude = 1/2
b. domain = all real numbers; period = π/2 ; range: - -6 ≤ y ≤ 6; amplitude = 6
c. domain = all real numbers; period = π/2 ; range: -6 ≤ y ≤ 6; amplitude = -6
d. domain = -1/2 ≤ x ≤ 1/2; period = 6π; range: -6 ≤ y ≤ 6 ; amplitude = 1/2