help regarding indexing and matching

hello, i am new to this forum, though in a few days i have got a grasp of a few concepts, i am still new to excel in general.

My problem is that i need help in indexing and matching,
my sample workbook would show it clearly,
in short,
i have 2 columns in sheet 1, with A giving the product name and b giving its value
and in sheet 2, i have Columns A & Column B which is essentially when put together gives the value of corresponding cells in column A,

i want a function which would give me the proper values in sheet 2 from sheet 1
...