All solutions here are SUGGESTED. Mr. Teng will hold no liability for any errors. Comments are entirely personal opinions.

(i)

Let X denote the number of batteries with lifetime of at least 100 hours, out of 10.

(ii)

(iii)

Let Y denote number of packs that satisfy the customer, out of 80.

Since is large,

approximately

by continuity correction

### KS Comments

Remember to do CONTINUITY CORRECTION!!!

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