If your speed changes from 10 km/h to 6 km/h, you have a(n) acceleration.. a.. negative. c.. neutral. b.. positive. d.. oscillating.

So if your speed changes from 10 km/h to 6 km/h, this means that you are des accelerating, so your velocity is decreasing. This will happen only if your acceleration is negative.

If your acceleration is positive, your velocity will increase, if your acceleration is neutral, then your velocity will be constant. If your acceleration is oscillating, then your velocity will decrease, then increase, then decrease, and so on.

see the picture for the vector

the magnitude of the vector by pythagorean theorem

r = √( (-10)^2 + (3)^2 ) = √109

magnitude = √109 units

the direction angle between vector and x-axis is

tan^(-1)(3/10) = 16.699

so the direction is approximately 16.7 degrees north of west

answer: 31, 5556. 952 seconds