For a large Internet service provider (ISP), Web virus attacks occur at a mean rate of 150 per day. (a) Estimate the probability of at least 175 attacks in a given day. (b) Estimate the probability of...

For a large Internet service provider (ISP), Web virus attacks occur at a mean rate of 150 per day. (a) Estimate the probability of at least 175 attacks in a given day. (b) Estimate the probability of fewer than 125 attacks. (c) Is the normal approximation justified? Show all calculations. (d) Use Excel to calculate the actual Poisson probabilities. How close were your approximations?