Answer:
Rubidium Acetate
Explanation:
Rb is Rubidium C2H3O2 is acetate
The bond order of BF₄⁻ is 1 and the bond order of BF₃ is 1.33
So, BF₃ is having more bond order than BF₄⁻.
In other words, BF₃ > BF₄⁻ ( You can write Bond Order or in B.O it's the abbreviation of Bond Order ).
I believe the cup within another would keep it warm the longest because it would insulate the heat within the main cup, that or you could just leave it in a microwave ^-^
Hope this sorta helps XD
