Write a method that returns how many factors of 2 a number has. For example, 40 has 3 factors of 2 because 40 can be factored into the primes 2*2*2*5. Some numbers do not have factors of 2, such as 13, 17, and 21. Other number has nothing but factors of 2, such as 64. In each case, return how many factors of 2 'num' has. As preconditions, you may assume that 'num' is non-negative. Look at the test data for examples.