Worst-case response time of the lowest task

Fixed-priority preemptive tasks (C, T) in priority order: T1 = (1, 4), T2 = (2, 6), T3 = (3, 12), deadlines equal to periods. Using response time analysis R = C3 + Σ ceil(R/Ti) × Ci, what is the worst-case response time of T3?