AMC 8 2020 Problem 11

After school, Maya and Naomi headed to the beach, $6$ miles away. Maya decided to bike while Naomi took a bus. The graph below shows their journeys, indicating the time and distance traveled. What was the difference, in miles per hour, between Naomi's and Maya's average speeds?

$\textbf{(A) }6 \textbf{(B) }12 \textbf{(C) }18 \textbf{(D) }20 \textbf{(E) }24$