Common ratio, r is found by dividing the next term by the previous term
r =

= -3
you can see this value is true for any consecutive pairs of terms
also, multiply by -3 to get the next term
B. 6 km
You have to draw it so you can better process it. From there it's just the Pythagorean theorum.
a²+b²=c²
6²+b²=10²
(10 is c because it's the hypotenuse)
64+b²=100
100-64=36
√36 = 6
111.
660/6 = 110. In order to make a profit you need to sell at least one more than that.
Hope this helps.