Match up (merge) 2 small spreadsheet into one (WILL AWARD ASAP)

I have a 250 row spreadsheet (a) that needs to merge with another spreadsheet (b). I have already added both spreadsheets (a&b) into one sheet. Your job would be to match up the both sides of this sheet based on "Entity Name" so that all the data is still there. (the 2 sides are seperated by a red shaded column) There should be about 175 of the rows that match up, the other rows you should keep or add as new. If you know excel and are good with data, you should be able to do this rather quickly. BUT keeping the matched up and lined up VERY IMPORTANT and one line off could throw my entire database project off. I am ready to award this NOW! Thanks