Can someone help me to answer this correctly, please, and explain it

For (C), the answers are below

The atomic weight of thulium ( Tm ) is based on its only naturally occurring isotope, which has an atomic mass of 168.93421000000 u. (a) Write the complete atomic symbol for thulium . How many protons, neutrons, and electrons are there in a Tm atom? protons neutrons electrons (b) Using the masses of the fundamental partices, estimate the mass of a thulium atom in atomic mass units by adding the masses of the particles that it contains. (c) Which of the two masses is larger? atomic mass sum of particle masses