The purchasing manager has formulated the following LP model:

Minimise COST = 6M1 + 5M2 + 4M3 + 7M4

subject to

0,05M1 + 0,04M2 + 0,08M4 50 (CHRM)

0,40M1 + 0,80M2 + 0,60M3 + 0,32M4 500 (IRON)

M1 + M2 + M3 + M4 = 1000 (MASS)

and all variables 0,

where Mi = number of kg of scrap type i purchased, i=1,2,3,4.

(a) Solve this model using LINGO or SOLVER.

(b) Write down the foundry's optimal purchasing plan an