  The Bekenstein-Hawking entropy of BPS black holes can be obtained as the
minimum of the mass (= largest central charge). In this letter we investigate
the analog procedure for the matrix model of M-theory. Especially we discuss
the configurations: (i) $2 \times 2 \times 2$ corresponding to the 5-d black
hole and (ii) the $5 \times 5 \times 5$ configuration yielding the 5-d string.
After getting their matrix-entropy, we discuss a way of counting of microstates
in matrix theory. As Yang Mills field theory we propose the gauged world volume
theory of the 11-d KK monopole.
