Please answer my test. Please give accurate answer. Thank you! The answer is only integers

Problem 20 Let a, b, c be real numbers such that Bab + 2 = 6b, 3bc + 2 = 5c, 3ca + 2 = 4a. Suppose the only possible values for the product abc are r/s and t/u, where r/s and t/u are both fractions in lowest terms. Find r + s + t + u. Answer to Problem 20 Problem 21 Find the sum of all positive integers n, 1 s n s 5000, for which n- + 2475n + 2454 + (-1)" is divisible by 2477. (Note that 2477 is a prime number.)