Selecting all rows in a master table and summing columns in multiple detail tables

I have a master table (Project List) along with several sub tables that are joined on one common field (RecNum). I need to get totals for all of the sub tables, by column and am not sure how to do it. This is a sample of the table design. There are more columns in each table (I need to pull * from "Project List") but I'm showing a sampling of the column names and values to get an idea of what to do.

Project List
| RecNum | Project Description |
|      6 | Sample description  |
|      7 | Another sample      |

WeekA
| RecNum | UserName | Day1Reg | Day1OT | Day2Reg | Day2OT | Day3Reg | Day3OT |
|      6 | JustMe   |       1 |      2 |       3 |      4 |       5 |      6 |
|      6 | NotMe    |       1 |      2 |       3 |      4 |       5 |      6 |
|      7 | JustMe   |         |        |         |        |         |        |
|      7 | NotMe    |         |        |         |        |         |        |

WeekB
| RecNum | UserName | Day1Reg | Day1OT | Day2Reg | Day2OT | Day3Reg | Day3OT |
|      6 | JustMe   |       7 |      8 |       1 |      2 |       3 |      4 |
|      6 | NotMe    |       7 |      8 |       1 |      2 |       3 |      4 |
|      7 | JustMe   |         |        |         |        |         |        |
|      7 | NotMe    |         |        |         |        |         |        |

So the first query should return the complete totals for both users, like this:

| RecNum | Project Description | sumReg | sumOT |
|      6 | Sample description  |     40 |    52 |
|      7 | Another sample      |      0 |     0 |

The second query should return the totals for just a specified user, (WHERE UserName = 'JustMe') like this:

| RecNum | Project Description | sumReg | sumOT |
|      6 | Sample description  |     20 |    26 |
|      7 | Another sample      |      0 |     0 |