The protocol data unit (PDU) for the application layer in the Internet stack is

In the IPv4 addressing format, the number of networks allowed under Class C addresses is

Consider a source computer (S) transmitting a file of size 10⁶ bits to a destination computer (D) over a network of two routers (R₁ and R₂) and three links (L₁, L₂, and L₃). L₁ connects S to R₁; L₂ connects R₁ to R₂; and L₃ connects R₂ to D. Let each link be of length 100 km. Assume signals travel over each line at a speed of 10⁸ meters per second. Assume that the link bandwidth on each link is 1 Mbps. Let the file be broken down into 1000 packets each of size 1000 bits. Find the total sum of transmission and propagation delays in transmitting the file from S to D?

An Internet Service Provider (ISP) has the following chunk of CIDR-based IP addresses available with it: 245.248.128.0/20.
The ISP wants to give half of this chunk of addresses to Organization A, and a quarter to Organization B, while retaining the remaining with itself. Which of the following is a valid allocation of address to A and B?