(i) Dynamic output resistance is given as: R0 = (ΔVCE/ΔIC)Iβ constant = 12V/(3.6mA - 7.4×10⁻³A) = 40.2 × 10³Ω = 20kΩ
(ii) dc current gain βac = IC/IB = 3.5mA/30µA = 3.5 × 10⁻³A / 30 × 10⁻⁶A = 116.67
(iii) ac current gain βac = ΔIC/ΔIB = (4.7 - 7.5)mA/(40 - 26)µA = 1.2 × 10³ × 10⁻⁶A = 120