HELPP PLSS I WILL GIVE U BRAINLIEST not really sure if this is supposed to be in the math section but its about graphs

i have this graph for science and i need to find the speeds but im not sure if im doing it right

the numbers that i have right now are

A) 0-8 = 8/2 = 4 m/m

B) 0-2.5=0/2.5=0m/m

C) 2.5-3=10/3=3.3m/m

D) 3-3.5=15/3.5=4.3m/m

m/m = miles per minute
and A, B,C, and D are like when what i think the speeds are of the four lines

((also if someone could help me on my other question in math that would be great)