You see a product of three sums in your expression, (a'+b) (a+b+c) and c'
you need to multiply them together to get a sum of products, then use and find the boolean identities (see the boolean rules for simplification section of the online textbook)and reduce the expression.If you try it in here we can help, but we won't give you the answer.
I think the original poster might either be asking for a way to simplify the expression and/or implementing the function using CMOS gates. However, I am not in the business of guessing. If the original poster will show that they have put some effort in trying to solve the problem, someone might be able to help. Seeing the word "urgent" is making me quite lazy ....