Complementary means something is hard
Log (7/4) is equivalent to log (7.7/4.4), therefore it's log(7.7) - log(4.4), or...
2.0142 - 1.4816 = 0.5326
Step-by-step explanation:

The distance traveled by the balloon in every minute makes an arithmetic sequence with a first term equal to 40 ft and common difference equal to 20. The nth term of an arithmetic sequence is calculated by,
an = a1 + (n - 1) x d
Substituting,
an = 40 + (15 - 1) x 20 = 320
Thus, the answer is letter B. 320 feet.