3. Four people are contributing to the entertainment section of an email magazine. For one issue reviews are required for a film, a musical, a ballet and a concert such that each person reviews one show. The people in charge of the magazine will pay each person's expenses and the cost, in pounds, for each reviewer to attend each show are given below.
| Film | Musical | Ballet | Concert |
| Andrew | 5 | 20 | 12 | 18 |
| Betty | 6 | 18 | 15 | 16 |
| Carlos | 4 | 21 | 9 | 15 |
| Davina | 5 | 16 | 11 | 13 |
Use the Hungarian algorithm to find an optimal assignment which minimises the total cost. State the total cost of this allocation.