Given a supply chain network which originates at three suppliers (R1, R2 and R3) and terminates at location T, where the other nodes (A-E) are transhipment points. Table Q3 shows the maximum amount of raw materials (in thousands) flow through each node per month.

Table Q3. Maximum amount of raw materials (in thousand unit) flow through each node

To From	A	B	C	D	E	T
R1	100	65	-	-	-	-
R2	40	100	-	-	-	-
R3	-	120	-	-	80	-
A	-	-	60	70	-	-
B	-	-	-	60	110	-
C	-	-	-	45	-	120
D	45	20	50	-	50	180
E	-	90	-	60	-	220

In addition to the maximum amount of raw materials allowed between each node, a minimum transporting requirement is also imposed between some transhipment points. For instance, Point D and E need to deliver at least 10 units and 5 units to Point C and D respectively.

1. Formulate the problem to determine the maximum amount of raw materials that can be transported per month. (20 Marks)

2. [EXCEL] Solve this problem using solver. (8 Marks)