Not sure if this is correct but i would choose the steel tray.
The average atomic mass of Boron: 10.431 amu
<h3>Further explanation
</h3>
Isotopes are atoms whose no-atom has the same number of protons while still having a different number of neutrons.
So Isotopes are elements that have the same Atomic Number (Proton)
Atomic mass is the average atomic mass of all its isotopes
In determining the mass of an atom, as a standard is the mass of 1 carbon-12 atom whose mass is 12 amu
Mass atom X = mass isotope 1 . % + mass isotope 2.% + ...
The average atomic mass of boron :

An ionic bond because ca is a metal and cl is a nonmetal which is an ionic bond
I have done some research as well as asking some friends. This is what I came up with. Not sure if it is 100% correct.
step = time after death
1. Livor Mortis = 20-30 minutes
2. Eyes film (cloud) = 2 hours
3. Rigor Mortis begins = 4-6 hours
4. Empty small intestines = 12 hours
5. Bloating = 3-5 days
6. Decay