I have two data sets.

data set a with group level data for variables x, y, and group_id.

data set b with individual level data for variables a, b and group_id. This data has duplicates of group_id. I want to add together var_a if group_id is the same and add together var_b if group_id is the same. To transform individual level data into group level data so I can merge it with data set a.

current data set b
group_id var_a var_b
1 100 60
1 50 10
2 30 20
2 10 70
3 110 130
I want it to look like:
group_id var_a var_b
1 150 70
2 40 90
3 110 130
I have tried to gen and egen new variables but have not been able to get anything to work. Any code or even the command to look at would be appreciated.