Text values to numeric in a new cell

Good evening.
After 3 hours I give up. Being a total newbie I have to surrender and ask for a litte help. I have a drop down in my spreadsheet with the values YES, NO, PARTIAL and N/A. Based on the selection I need to make numeric output to another cell where YES=100, NO=0, Partial=50 and N/A="" (I need the values to calculate some scoring) I have been looking a lot at the IF function, but fail to understand how to use several values. Any idea are highly appreciatedplease....

Thank you soo much shg. I will try it right away..

Dear Shg - I feel stupid. I canīt figure it out. I have attached the simple spreadsheet. Can you show me how to make it work?. Sorry...