(a) The area to the left of $Z=0.15$ is (Round to four decimal places as needed.)

Step 1 ：The area to the left of a Z-score in a standard normal distribution represents the cumulative probability up to that Z-score. We can calculate this using the cumulative distribution function (CDF).

Step 2 ：Given a Z-score of 0.15, we can calculate the area to the left of this Z-score.

Step 3 ：Using the CDF, we find that the area to the left of Z=0.15 is approximately 0.5596176923702425.

Step 4 ：Rounding this to four decimal places, we get 0.5596.

Step 5 ：\(\boxed{0.5596}\) is the final answer.