please help I'm stuck. 
I'm trying to solve this. 

![enter image description here](https://i.stack.imgur.com/BGfTC.jpg)

so far I have:   

a) a+b+c   

b) a+bc   

c) a+b   

d) a+b   

but for e) I can't progress further since I don't know how to deal with a'bc in this case. 
anyone so kind to please help me?