An ISP that has authority to assign addresses from a /16 prefix

(an old class B address) is working with a new company to allocate it a portion of address space based on CIDR. The new company needs IP addresses for machines in three divisions of its corporate network: Engineering, Marketing, and Sales. These divisions plan to grow as follows: Engineering has five machines as of the start of year 1 and intends to add one machine every week; Marketing will never need more than 16 machines; and Sales needs 1 machine for every two clients. As of the start of year 1, the company has no clients, but the sales model indicates that by the start of year 2, your company will have six clients and each week thereafter, it gets one new client with probability 60%, loses one client with probability 20%, or maintains the same number with probability 20%.

(a) What address range would be required to support the company’s growth plans for at least 7 years if Marketing uses all 16 of its addresses and the Sales and Engineering plans behave as expected?

(b) How long would this address assignment last? At the time when the company runs out of address space, how would the addresses be assigned to the three groups?

(c) If instead of using CIDR addressing, it was necessary to use oldstyle classful addresses, what options would the new company have in terms of getting address space?