B it is ,

you don't need to complete calculation if you see there is some cord which is connecting the two discs and and two sectors are left free without cord .

calculate disc 1 = 270/360 * 2* pi*80

cl . disc 2 - 270/360 *2 * pi* 60

= 90pi + 120 pi = 210 pi + the extra length

if look at the choice there is only once choice which is 210 oi + extra B

so the rest you need not calculate .

let me know if their is any flaw in my reasoning .

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---- Hero never chooses Destiny

Destiny chooses Him ......