Chapter 5.9, Problem 5.20P

The synthetic antiviral drug Tamiflu, currently the most effective agent against avianinfluenza, is prepared by a 10-step synthesis. What is the overall yield of Tamiflu in each ofthe following 10-step syntheses?
a. Each step proceeds in $90.\%$ yield.
b. Each step proceeds in $80.\%$ yield.
c. One step proceeds in $50.\%$ yield, while the rest occur in $90.\%$ yield.
d. The following yields are recorded: 20.% (one reaction), $50.\%$ (two reactions), $80.\%$ (all remaining reactions).