Answer:The thymus stores and produces T lymphocytes and also releases hormones which aid in the maturation of the T lymphocytes while the spleen stores and release lymphocytes as well as macrophages which eradicate foreign substances that may harm the body.
Explanation:
Seems to me that it flies 400 m/s there and 600 m/s back the same distance.
therefore the average of 400 and 600 is 500 m/s. The distance is the same so the normal formula of (d2-d1)/(t2-t1) is applicable.
You would most likely be witnessing an eclipse
500m has 1 significant digit.