Review the following information about vectors q and r. q = ⟨–4, 1⟩

r = ⟨a, 3⟩

7(q + r) = ⟨–35, 28⟩

What is the value of a?

–31
–7
–5
–1

Study results indicate that the mean length of time people spend on a bus in a city is between 21.2 min and 24.5 min what is the study margin of the error?