Holding a population of microorganisms having a z value of 1

Holding a population of microorganisms (having a z value of 17 F) at 243 F for one minute has the same lethal effect as holding the population at 250 F for the following minutes: (select the correct answer – answers may be rounded).

Solution

Lethal rate = 10 (250-243)/17OF
Answer: 2.57
Lethal effect/rate can be calculated by the equation:
Lethal rate = 10 (T-Tr)/z
Hence by applying the equation, L= 10 ^ (250-243)/17OF
L = 10^7/17
L= 10^0.411
L= 2.57