Making expressions and inqquality constraints from "a story".

Ok this is the question.. (it requires use of the Simplex Algorithm) Please help! It's due tomorrow!

**Note: Only the thing i want to maximize and the constraints are needed! No need to trouble you with the whole simplex algorithm :p

__Question:__

Three processes, I, II and III and involved in the manufacture of three products, A, B and C. For each product, the manufacturing time (hours) and profit per item (£) are as shown.

__Product---I---II---III---Profit__

--A------1---2---3---120

--B------5---1---2---70

--C------4---4---1---100

The total manufacturing times on processes I, II, and III are 90, 35 and 60 hours respectively.

a) What mix of products yields the greatest profit?

b) What assumptions have you made in answering part (a)?