Hello there
1) asthenosphere lies below lithosphere and part of uppermantle.
it's highly viscous and behaves plastic.
it lies approximately 70-150 km below surface depending which . (50km below oceanic crust and 150km below continental crust)
2) 1/2 '4 =1/16 (4 is to the power of 1/2)
hope this helps
thank you
Best Regards Queen Z