The number of mosquitoes in a field after a major rainfall is modeled by the function M defined by M(t)=−t3+12t2+144t , where t is the number of days after the rainfall ended and 0≤t≤18 . Using correct units, interpret the meaning of M′(15)=−171 in the context of the problem.

Two trains leave a station on different tracks. the tracks make an angle of 130°, with the station as a vertex. the first train travels 100 km and makes its first stop at point a, while the second train travels 200 km and makes it first stop at point b. how far apart are the trains when both are at their first stop? round the answer to the nearest integer. a) 65 km b) 139 km c) 224 km d) 275 km