i am working on a paper about the mafia in italy.

my equation:
Y=beta0 + beta1*MPI + beta2*Controls

Y = Response Rate in a given city (an outcome conducted in an experiment)
MPI = Mafia presence Index (0-100), measuring the presence of the mafia in a given city.

the effect of the MPI is significant, all good even if i control.

now my question:
can i include dummies, taking the value 1 if the corresponding mafia group is present in a city, in order to find out which group has the biggest influence on Y, i.e. just a more detailed analysis of the mafia presence effect.

it would then look like this:
Y=beta0 + beta1*MPI +beta2*Camorra +beta3*Ndrangheta + beta4*CosaNostra+ beta5*Controls

or do i need to exclude the MPI or even use a different approach?

thanks for your help!