A production process uses a $2-$step operation. Tomorrow's work will consist of seven orders as shown below. Determine a job sequence that will minimize the total time required. What is the minimum total time?

a$.$

$12\mathrm{.}95$

b$.$

$12\mathrm{.}55$

c$.$

$13\mathrm{.}45$

d$.$

$13\mathrm{.}15$