Excel If function I think

Hello,

I have a set of data in Column A where the policy numbers comes in three formats

1) 7000055555-03
2) 012222222-00
3) 001111111-00

After running an extractnumber function my output in Column B is this:

1) 700005555503
2) 1222222200
3) 111111100

What I want is in Column C to reference if the data starts with a 7 in column A, then to pull the left 10 digits in column B, if the data in column A starts with 01, then to pull the left 8 digits from column B, and then if the data in column A starts with 00 to pull the left 7 digits in column B.

Any help would be appreciated!