HELP Needed on welding problem

Hi need to calculate solve this question but I could not get the proper way to solve this..

Can anyone suggest some ways to salve these

The ability of the heat source to melt the base metal is an important consideration in fusion welding.

Melting efficiency (as distinct from energy transfer efficiency, h) is defined as follows:

Use the data in Table to calculate the energy need to melt 1 mm³ of carbon steel (starting at 20 °C).

Hence find the minimum power needed to generate a bead on plate weld of 15 mm² cross sectional area in carbon steel at a welding speed of 4 mm/s.

For this weld, the actual power input was 2 kW. Calculate the melting efficiency.

TABLE

r density/ kg m^-3

C_m specific heat per unit mass/ kJ kg^-1 K^-1

C_V specific heat per unit volume/ kJ m^-3 K^-1

DH_m latent heat of melting per unit mass/ kJ kg^-1

T_m melting temperature/ °C

l thermal conductivity / W m^-1 K^-1