There Are Four Resources and Four Jobs to Be Done

Multiple Choice

There are four resources and four jobs to be done. The time required for each resource to do each job is as follows: $$\begin{array} { c } \quad \quad \quad \quad { \text { Job (Hours) } } \\\begin{array} { l c c c c } \text { Resource } & \mathrm { A } & \mathrm { B } & \mathrm { C } & \mathrm { D } \\\hline 1 & 5 & 8 & 7 & 7 \\2 & 4 & 9 & 5 & 9 \\3 & 6 & 9 & 8 & 7 \\4 & 7 & 6 & 6 & 9\end{array}\end{array}$$ For the optimal schedule, what is the total number of hours required to complete these jobs?

A) 23 hours
B) 22 hours
C) 21 hours
D) 20 hours
E) 19 hours