To find the probability that the employee will arrive between 8:05 a.m. and 8:40 a.m., we need to determine the length of the interval between 8:05 a.m. and 8:40 a.m. out of the total length of the interval between 8:00 a.m. and 8:50 a.m.
The length of the interval between 8:00 a.m. and 8:50 a.m. is 50 minutes (8:50 a.m. - 8:00 a.m. = 50 minutes).
The length of the interval between 8:05 a.m. and 8:40 a.m. is 35 minutes (8:40 a.m. - 8:05 a.m. = 35 minutes).
To determine the probability, we divide the length of the interval between 8:05 a.m. and 8:40 a.m. by the length of the interval between 8:00 a.m. and 8:50 a.m.:
$$\text{Probability} = \frac{\text{Length of interval between 8:05 a.m. and 8:40 a.m.}}{\text{Length of interval between 8:00 a.m. and 8:50 a.m.}}$$
$$\text{Probability} = \frac{35}{50}$$
Simplifying,
$$\text{Probability} = 0.7$$
Answer: The probability that the employee will arrive between 8:05 a.m. and 8:40 a.m. is 0.7.