The head chef A can cook one dish in 4 minutes,
while his fellow chef B can finish in 8 minutes,
but a young chef C has an unknown capability.
Then two more chefs are hired into the team:
chef D can cook one dish in 6 minutes, and
chef E in 9 minutes.
If the average cooking time per person before and after the new hiring is unchanged, in how many minutes can chef C cook one dish?