Correct answer: 5 A
The efficiency equation is η = (VsIs) / (VpIp). Rearranging for Ip, we get Ip = (VsIs) / (ηVp). Substituting η = 0.9, Vs = 450 V, Vp = 3000 V, and assuming Is = 1 A (not explicitly given but implied for simplicity), Ip = (450 * 1) / (0.9 * 3000) = 5 A.