Given the following information on job times and due dates.

Job Job Time (Hours) Due Date (Hours)
a 3.5 7
b 2.0 6
c 4.5 18
d 5.0 22
e 2.5 4
f 6.0 20

Determine the optimal processing sequence using:

a. First come, first served
b. Shortest processing time
c. Earliest due date.
d. Critical ratio.