The demand for printed books is a random variable D with distribution approximated by a continuous uniform distribution on the interval[20,60]. Each book printed costs $15 to produce and sells for $33. Any books left unsold will be disposed of at a cost of $10 per book plus a fixed disposal fee of $80. If a copy of the book is unavailable then a copy will be fast printed but this will cost the bookshop $50 instead of the usual $15. How many books should be printed at the start to minimise expected costs?