A mine workshop needs to assign 4 jobs to 4 service engineers. The cost for performing a job by an individual service engineer is given. A typical job can be assigned to only one service engineer. If the service engineer S1 cannot perform the job J3, and S3 cannot perform the job J4, the optimal cost for completion of jobs is
.
(answer in integer)
| Service Engineer | J1 | J2 | J3 | J4 |
|---|
| S1 | 50 | 50 | --- | 20 |
| S2 | 70 | 40 | 20 | 70 |
| S3 | 90 | 30 | 50 | --- |
| S4 | 70 | 20 | 60 | 30 |