Aron is training for a 10 km marathon swim in 19 weeks.  Each week, his training plan includes a long distance swim.  In week six, Aron swam a total of 18.75 km.  In week ten, Aron swam a total of 36.25 km.  Each week, Aron increased the distance he swam following an arithmetic sequence until the final week.  In the last week, Aron only swam 5 km in order to save energy for the race. 

a. By what distance did Aron increase his total swimming each week?

 

b. Determine the distance Aron swam in the first week of training.

c. Determine how far Aron swam in the 18-week training program