Problem
Suppose M1 is a two-tape TM, and M2 is the ordinary TM constructed in to simulate M1. If M1 requires n moves to process an input string x, give an upper bound on the number of moves M2 requires in order to simulate the processing of x. Note that the number of moves M1 has made places a limit on the position of its tape head. Try to make your upper bound as sharp as possible.