What is the total amount of heat required to completely melt 347 grams of ice at its melting point?

Can someone me with questions 15 to 17 plz.

Americium-241 undergoes fission to produce three neutrons per fission event. if a neutron-absorbing material is mixed in with this sample so that the rate of neutron production drops down to 1.8 neutrons per fission event, which will be effective at achieving a critical mass? check all that apply. remove a deflective shield surrounding the sample. remove absorbent material mixed in with the sample. compress the sample of americium-241.

Which factor is likely to impact the possible number of compounds ?