GO THRU THIS ONE...

I dont know what is eqn 17.13..........

but I am replying to rest of the parts.....

v_o= 0
f'=[v/v-v_scosθ]f

But cosθ=4/5
so, f'=[343/343-0.8(25)]500 =531 HZ

Since 0<θ<180
so, f']_max=[v/v-v_scos0]f =539HZ
& f'_min=[v/v-v_scos180]f=466HZ

Since source and observer moving away from each other
so,θ_o-θ_s=180........Is this hint enough.????

u r welcome.