This is a non common compound. In fact, I found that it is a new compound.
Boron is a metalloid which means that it can form compounds with transition elements (copper is a transition elements).
Cupric means that copper is with its highest oxydation state, 2+. Oxydation state of boride is 3-
I found the chemical formula is B2Cu3 (2 and 3 are subscripts).
That is the formula I found written.I am not sure why they write it with the B at left. The rule is to put the more electroneative element to the right. B's electronetativity is 2.04 and Cu's electronegativity is 1.90, although they are very close, Cu is less electronegative than B, then the formula should be written as Cu3B2.
Anyway, that doesn't make any difference about the properties and the chemistry of the compound.
Based on the regular rules, the prediction of the formula is Cu3B2, and that should be the answer.
Answer: Cu3B2 (equivalent to B2Cu3)