FILTER function output, replace 1st character of each item in field

[craigexcel]

I'm working with SAP data, which includes Cost Center (numeric), Activity Type (alphanumeric), and rates.
Cost Centers are like 210000, 210010, 210020, and 210030.
Activity Types are like 1AACA1, 1ACOC2, 1ANBC0, 9AACC2, 9ACON2, 9ASSP1.

I create a pivot table to include these 3 elements. The item in the "Row" field of the pivot table is concatenated, like 210000_1AACA1. (It could just as easily be 2 separate fields, instead of a concatenated value, if that would better support a solution for this.) The concatenated items can be any combination of Cost Center and Activity Type (1????? and 9?????).

The problem I'm trying to solve is this: I have taken the approach to try to use the FILTER function on the pivot table data to get the data I want. The rates for all 1????? and 9????? Activity Types need to remain as is, but for any 1????? Activity Type only, I also need (in the result), converted values like 2?????, with an associated overtime rate calculated as the base rate * 1.5.

It would be ideal if this could all be incorporated in the pivot table results, but as referenced, if that doesn't seem possible, the FILTER function works too.

example pivot table data (since I don't have the ability @ work to download the tool to include the Excel data image):

Cost Ctr Act Type Rate
210000 1AACA1 10.00
210000 9AACC2 15.00
210010 1ANBC0 12.00
210030 9ASSP1 16.00
210000 2AACA1 15.00 (210000 / 1AACA1 $10 rate * 1.5)
210010 2ANBC0 18.00 (210010 / 1ANBC0 $12 rate * 1.5)

Windows 10 Enterprise
64-bit
Office 365

I tried using the REPLACE function for the 'include' argument of the FILTER function, using <Ctrl><Shift><Enter>, without success.
I would appreciate any thoughts you may have to solve this, or resources that might suggest some ways to do this. Thanks.