Given the data below, using the SPT sequencing rule, determine the completion date and tardiness for each job as well as the average completion time and average tardiness for all four jobs. Which of the following statements is true?

Job A: processing time $($days$)=10,$ due date $($in days$)=10$

Job B: processing time $($days$)=5,$ due date $($in days$)=8$

Job C: processing time $($days$)=15,$ due date $($in days$)=25$

Job D: processing time $($days$)=8,$ due date $($in days$)=15$

A$.$ The average tardiness is $19\mathrm{.}75$

B$.$ The average completion time is $6\mathrm{.}5$

C$.$ Jobs B and D will have no tardiness

D$.$ The tardiness for Job A is $12$ days