The subnet mask on the serial intece of a router is expressed in binary as 11111000 for the last oct

The subnet mask on the serial intece of a router is expressed in binary as 11111000 for the last octet. How do you express the binary number 11111000 in decimal?（） A. 210 B. 224 C. 240 D. 248 E. 252

To convert the binary number 11111000 to decimal, we calculate the sum of each bit's value based on its position. An 8-bit binary number (octet) uses powers of 2 from $2^0$ (rightmost bit) to $2^7$ (leftmost bit).

For the binary number 11111000:

The leftmost 5 bits are "1", corresponding to positions 7 to 3 (from left to right).

Their values are: \(2^7=128\), \(2^6=64\), \(2^5=32\), \(2^4=16\), and \(2^3=8\).

Summing these values: \(128 + 64 + 32 + 16 + 8 = 248\).

Answer: D. 248