plz give me the solution of qes.no 6? correct ans is 1.71p (density)rc

[In the given problem fall in temperature of body dT=(200−100) = 100K, temp. of surrounding T0 = 0K, Initial temperature of body T = 200K].
100dt=σ4πr243πr3ρcJ(2004−04)
Þ dt=rρcJ48σ×10−6s=rρcσ.4.248 × 10−6
=780rρcσμs~772rρcσμs
[As J = 4.2]