Need help with the bold part !

Consider a packet of length L, which begins at source and travels over seven links to a destination. These links are connected through six routers. Let di, si, and Ri denote the length, propagation speed, and the transmission rate of link i, for i = 1 to 7. The processing delay at each router is d-proc. The queuing delay at each router is d-que. What is the total end-to-end delay for the packet in terms of di, si, Ri (i = 1 to 7), and L?

Now suppose, the packet is 2,500 Bytes, the propagation speed on all links is 2.5x108 m/s, the transmission rates of all links are 1.6 Mbps. The length of first and second links are 5,000 Km, the length of third, fourth, fifth and sixth links are 4,000 Km, and the length of seventh links is 1,000 Km. Processing delay in each router is 2 msec (mili-second) and queuing delay in each router is 7 msec. For these values, what is the end-to-end delay? Write down your calculations.