A solid object of mass M is made from a material of specific heat capacity C and specific latent heat of fusion L and of very high thermal conductivity enters the atmosphere from
outer space, its temperature being below its melting point by !:!T. Because of atmospheric friction it absorbs energy at a constant rate R. The time before the solid becomes
completely molten is given by:

• A

  $\frac{\mathrm{M}(\mathrm{C}+\mathrm{L})∆\mathrm{T}}{\mathrm{R}}$

• B

  $\frac{\mathrm{M}(\mathrm{C}∆\mathrm{T}+\mathrm{L})}{\mathrm{R}}$

• C

  $\mathrm{M}(\mathrm{C}+\mathrm{L})∆\mathrm{TR}$

• D

  $\frac{\mathrm{R}}{\mathrm{M}∆\mathrm{T}(\mathrm{C}+\mathrm{L})}$