5. Defects occur at random in planks of wood with a constant rate of 0.5 per 10 cm length. Jim buys a plank of length 100 cm .
- Find the probability that Jim's plank contains at most 3 defects.
Shivani buys 6 planks each of length 100 cm .
- Find the probability that fewer than 2 of Shivani's planks contain at most 3 defects.
- Using a suitable approximation, estimate the probability that the total number of defects on Shivani's 6 planks is less than 18.