Biochemical engineering question 2?

[michaelespiritu31]

In a 1000 liter vessel operating at 80% capacity, it takes 10 minutes to reduce the vegetative cell population by one fifth and twenty minutes to reduce the spore population by the same ratio.

If the spore population is initially 1000 per centimeter cube (cm^3) and vegetative cells were 15000 per centimeter cube (cm^3), the effeciency of sterilization if such were carried for 30 minutes is??