The dotted blue line shows the path of lane 6 to where the track goes from 6 lanes to 10 lanes.
2s+πd=300 (inner perimeter), s=½(300-πd).
Area of central plot=sd+πd²/4.
Outer area=s(d+16l)+π(d+16l)²/4.
Track area=16ls+8πl(d+8l).
Substitute for s: 8l(300-πd)+8πl(d+8l)=2400l+64πl².
Plug in l=1.2: 2880+92.16π=3169.53 sq m=34116.5 sq ft. approx.