Excel Formula/Equation for Finding How Many Units can fit in a Box (Hard)

Question

Column A = Units, Column B = Box and need to find Column C = Box2

Unit   Box   Box2
2      11    10(need a formula here to calculate this)
3      10    9
4      10    8

I need Column C to suggest appropriate box size to fit most possible units.
so for C2, since 11/2 = 5.5, so the box should suggest 10 to make a perfect fit.
for C3, 10/3 =3.33 so 9, and 10/4 = 2.5, so 8 and not 12.

Answer 1

FLOOR would also work

=FLOOR(B2,A2)

Answer 2

In cell C2 and copied down:

=INT(B2/A2)*A2