Measure exactly 4 ml without reaching 3 ml in either cup.

In the basement of the laboratory, mandrakes are cultivated, and there is an unlimited supply of mandrake extract. Using the 5 ml and 7 ml measuring cups from problem 2, how can you measure exactly 4 ml of extract? However, take care! At no point may either cup contain exactly 3 ml — otherwise, the mandrakes will scream and wreak havoc in the laboratory.