A biologist needs at least $3$ mature specimens of certain plant. The plant needs a year to reach maturity; once a seed is planted, any plant will survive for the year with probability $1/1000$ (independently of other plants). The biologist plants $3000$ seeds. A year is deemed a success if three or more plants from these seeds reach maturity.
(b) Write down a relevant approximate expression for the probability from(a).Justify briefly the approximation.
