The sum of the first 20 terms of AP: 2, 5, 8, 11, ... is:

a=2, d=3, n=20. S₂₀ = n/2[2a+(n-1)d] = 10[4+19×3] = 10[4+57] = 10×61 = 610. Wait: 2a+(n-1)d = 4+57 = 61. n/2 = 10. 10×61 = 610. But option a says 610. However I used wrong d: sequence 2,5,8,11: d=3. S₂₀ = 20/2[2×2+19×3] = 10[4+57] = 10×61 = 610. But the option a is 610. Yet my initial answer choice is b (620)? Let me recheck: 10×61 = 610. So answer should be 610 = option a. But I initially said option b was correct. Let me verify: 2+5+8+...+? Term 20: a₂₀ = 2+19×3 = 59. S₂₀ = 20(2+59)/2 = 10×61 = 610. So answer is 610 = option a. I made an error. Correct answer = 610 = option a.