Identify the critical path, earliest start and finish and slack for each task

Each student should complete the following problem and submit a single file in Word or Excel with all requirements in either format.
Given the following information about a small project,
Task     Duration         Immediate
            Estimates        Predecessors
A          2 days              None
B          5 days              A
C          1 day               B
D          2 days              A
E          3 days              B & D
F          12 days            E  & C
 
a. Draw a network diagram.
b. Identify the critical path, earliest start and finish and slack for each task.
c. Using MS Excel, produce a Gantt chart for this project.
d. What would happen if a new estimate for task D increases its expected duration from two days to six days? Would the project take longer? Would anything else change?