Answer:
0.15 etc.
Step-by-step explanation:
The graph of the equation given by y=-cos³θ will be as follows:
You would need more details like the y values or something. Rate of change is slope though if that helps you enough to figure it out
First we need to find out the time it took for the truck to reach town B.



Now, because the van left 1.5 hours earlier and reached the destination 2.5 hours before, it took 1 hour less the the truck to arrive.

which is the time it took for the van to arrive.
Now we use the speed equation again to work out speed.


= speed of van
Hope this helped :)