offers
a
1
40
a
2
45
a
3
10
a
4
30
requests
b
1
35
b
2
70
b
3
10
b
4
10
The
minimum
cost
is
525
20
0
10
10
0
45
0
0
0
10
0
0
15
15
0
0
an
optimal
plan
cost
matrix
c
11
6
c
12
4
c
13
2
c
14
1
c
21
5
c
22
2
c
23
1
c
24
1
c
31
9
c
32
6
c
33
6
c
34
4
c
41
9
c
42
6
c
43
6
c
44
4
