Addition of all Sides of Given figure is called perimeter
∴ Perimeter of the given figure =(200+300+80+300+200+260)m=1340 m
∴ Total cost of fencing it at the rate of Rs.20 per meter
=Rs.(1340×20)=Rs.26800
∴ Area of the flower bed =(100×80)m2=8000 m2
Now, cost of manuring the flower bed at the rate of Rs.50 per square meter =Rs.(50×8000)=Rs.400000.