Participating in a human rally wave at a football game, you have to stand up every \(15 \mathrm{~s}\).

(a) What is the wave frequency?

(b) If the stadium is oval and the inner circumference of the oval is \(0.56 \mathrm{~km}\), what is the wave speed? Assume that the main wave pulse spans 30 people and that the distance between the heads of any two adjacent people is \(1.0 \mathrm{~m}\).