The accompanying figure shows a network of one-way streets with traffic

flowing in the directions indicated. The flowrates along the streets are

measured as the average number of vehicles per hour.

(a)

Set up a linear system whose solution provides the unknown flow rates.

(b)

Solve the system for the unknown flow rates.

(c)

If the flow along the road from A to B must be reduced for construction,

what is the minimum flow that is required to keep traffic flowing on all

roads?