Suppose you typed a URL in your browser and clicked "Return" button. This URL hasn't been visited locally before. Therefore, the system needs to use DNS protocol to find the IP address. Assume the request need to visit n servers to find the IP address, the round$-$trip time for each server is RTT$1,$ RTT$2,$ RTT$3,...,$ RTTn$.$ On the webpage, it only contains a very small picture, which we can ignore the time cost of data transmission. The round$-$trip time from your local machine to the web server is RTTw$.$

$1.$ How long it takes to load the just small picture?

Assume on the webpage, it contains $3$ objects. All of them are very small so that we can ignore the time cost of data transmission.

$2.$ How long it takes to load the whole webpage with non$-$persistent HTTP$?$

$3.$ How long it takes to load the whole webpage with concurrent $($parallel$)$ non$-$persistent HTTP$?4.$How long it takes to load the whole webpage with persistent HTTP$?$