Suppose there are $4$ routers connected between two systems $S_1$ and $S_2$. $S_1$ wants to send a python file of size $8 \:KB$ to $S_2$. But the data rates at each routers are different. The data rates between the routers are $1 \: Mbps$ , $2 \: Mbps$, $1 \: Mbps$ and $512 \: Kbps$ respectively. Find the maximum possible bandwidth for the file transfer in Kbps.

(Assume that the time to transfer $1$ bit from $S_1$ to $S_2$ is $32$ sec and there is no traffic between these two systems)