Task: Question Understanding
Input (English): Let u(n) = 5 + 3*n**3 - 4*n**3 + n + n - 3*n**2 + 7*n**2. Suppose 0 = -4*i - 2*t + 20, 3*i - 18 + 0 = -3*t. What is the units digit of u(i)?
Output (English): numbers