Excel formula - Urgent

I need create a quoation form but the price will change from different factors.

e.g. item 103 have 4 size, each size has different price

If I input the cell A1 is 103 and B1 is size 1. cell C1 can show the price is 10
If I input the cell A2 is 103 and B2 is size 2. cell C2 can show the price is 15


Please advise any formula can auto show the correct price