Question needed answered is the following

Does it cost extra to repair a truck as it gets older? If so, how much? How much does mileage contribute to repair expenses?

Case 1: Long Haul Trucking Company. Rick, I am disappointed that the diesel trucks have not produced the operating savings we expected. They are very costly to maintain. Charlie Gore, the Fleet manager for Long Haul Trucking Company was talking to Rick Sanchez, the purchasing manager for Long Haul Trucking. Long Haul Trucking operates a fleet of trucks to deliver merchandise from warehouses to retailers. A few years ago, faced with rising maintenance and fuel costs, the company purchased some diesel trucks for its fleet because it had heard that these trucks were more economical to operate. This is because, on average, diesel fuel is 12 cents per gallon cheaper than gasoline and the average truck gets 10 miles per gallon. The manager of the truck fleet, Charlie Gore, however, has been reviewing the repair and maintenance bills for the trucks and has found that the diesel trucks seem to be more expensive to repair and maintain than the regular gasoline-powered trucks. He has collected the repair and maintenance (R&M) expense for this last year on the entire fleet of 20 trucks by their age, miles driven, and type. The data is summarized in Table 1 on the next page. Rick, said Charlie as he put the data in Table 1 in front of Sanchez, this data shows that, on average the 6 diesel trucks cost $21,156 in R&M expense whereas the 14 gasoline trucks averaged only $13,269 in R&M expense. I am also surprised that simple correlations show a negative relationship between miles driven and age and between miles driven and type of truck. Rick looked up at Charlie and replied, Charlie can I borrow this data. I have a young college graduate that I just hired and and she is very bright. Let me ask her to look at this data and see what she comes up with.

Table 1 Annual Repair and Maintenance Cost for Trucks

Truck #	Expense	Miles	Years	Type
1	21,100	100,625	1	Diesel
2	23,548	108,750	2	Diesel
3	18,560	83,438	2	Diesel
4	19,525	77,500	3	Diesel
5	22,435	88,125	3	Diesel
6	21,768	85,938	3	Diesel
7	10,345	95,625	1	Gas
8	11,575	91,875	1	Gas
9	14,240	98,125	2	Gas
10	13,300	88,438	2	Gas
11	14,105	90,625	2	Gas
12	13,050	81,875	2	Gas
13	17,150	95,625	3	Gas
14	11,230	76,849	2	Gas
15	10,490	92,145	1	Gas
16	16,645	86,940	3	Gas
17	16,219	91,257	3	Gas
18	13,565	85,432	2	Gas
19	9,245	84,688	1	Gas
20	14,600	80,625	3	Gas

* can you please provide detailed explanation for a better comprehension.