題組內容
2. (20%) Each of four persons fires one shot at a target. Let \( C_k \) denote the event that the target is hit by person \( k, k = 1, 2, 3, 4 \). If \( C_1, C_2, C_3, C_4 \) are independent and if \( P(C_1) = P(C_2) = 0.7 \), \( P(C_3) = 0.9 \), and \( P(C_4) = 0.4 \), compute the probability that
(d) at least one hits the target.