During a cargo raid, the customs team discovers 8 crates of illegal tobacco. The weights of the first 7 crates are: 42 kg, 45 kg, 38 kg, 44 kg, 41 kg, 40 kg, and 43 kg. If the average (arithmetic mean) weight of all 8 crates is 42 kg, what is the weight of the 8th crate?