Lice are pesky problem for children and is unrelated to cleanliness. The lifetime of lice which have fallen off scalp on bedding is aprox normal distributed with a mean of 2.2 days and a standard d of 0.4 days what % of lice live
1. between 1.8 and 2.6 days
2. more than 3.0 days
3. between 1.5 and 2.5 days