Problem: four horses are tethered at 4 corners of a square field of side 70 metres so that they just can not reach one another . the area left ungrazed by the horses is : 
Options: ['a ) 1050 sq . m', 'b ) 3850 sq . m', 'c ) 950 sq . m', 'd ) 1075 sq . m', 'e ) 1065 sq . m']
a