$28-2.$ A mallet is hitting a steel beam. The beam is hit $50$ times in $14$ seconds at a constant rate. Take the speed of sound in air to be $340\frac{m}{s}$ and in steel to be $5000\frac{m}{s}.$

a$)$ What is the frequency of the pulses through the beam?

b$)$ What is the wavelength of the pulses through the beam?

c$)$ What is the frequency of the pulses in the air?

d$)$ What is the wavelength of the pulses in the air?