Part (b) requires an explanation, not a calculation.  But appropriate equalities can be written out as such!

Parts (a) and (c) will involve solving differential equations to get formulas for functions of  t  and then using the resulting formulas appropriately.

Your group is collectively responsible for the group project, and your group should submit one document
with the names of all the group members on it.  That document should have at most two pages of explanation and calculations, though it may have a graph or picture in addition.

Everyone in a group will get the same grade on the project.