Hot steel sphere of diameter 40mm is immersed in oil. If the heat transfer coefficient between the sphereand oil is 300 W/sqm K , then Biot Number is:(Take $$k_{steel}$$ = 50 W/m K and $$k_{oil}$$ = 0.2 W/m K)

A

0.04

B

0.12

C

10

D

0.24