In grade school, you learned to multiply long numbers on a digit-by-digit basis, so that 127 × 211 = 127 × 1 + 127 × 10 + 127 × 200 = 26, 397. Analyze the time complexity of multiplying two n-digit numbers with this method as a function of n (assume constant base size). Assume that single-digit by single-digit addition or multiplication takes O(1) time.