Broadcasting a message in a fully connected network

Computer Science Level 3

In a fully connected network with $n$ nodes, the number of direct links between all pairs of computers is $\frac {n(n-1)} 2.$ For $n = 2000$ , find the minimum time required to broadcast a message stored in $P_1$ to all other computers in the network. Assume that

sending a message from a computer to another computer takes $10^{-6}$ sec;
any computer can send only one message to any other computer at a time.

Here is an example of fully connected computers with 8 computers.

11 \times 10^{-6}

sec

1.9

sec

1

sec

20 \times 10^{-6}

sec

500 \times 10^{-6}

sec