A Project Scheduling Problem

Part 1:  Widgetco is making a prototype of a new product.  The product consists of two subassemblies.  Before building either subassembly, the firm must purchase raw materials and train workers.  Before the subassemblies can be combined, subassembly 2 must be inspected.  The following table describes the project:

Activity Description Requires Duration (Days)
A Train Workers -- 6
B Purchase Materials -- 9
C Make Subassembly 1 A, B 8
D Make Subassembly 2 A, B 7
E Inspect Subassembly 2 D 10
F Combine Subassemblies C, E 12
G Subassembly 2 Safety Report E 6

How quickly can Widgetco complete this project?

Part 2:  Management imposes a deadline of 25 days to complete the project.  Fortunately, each of activities may be shortened by up to 5 days at the following cost per day:

Activity Cost to
Shorten by
One Day
A $10
B $20
C $3
D $30
E $40
F $50
G $15

What is the cheapest way for Widgetco to complete the project in 25 days?