query about place of supply and gst applicability

samirshaikh (Account executive) (35 Points)

06 January 2019  
Dear sir,
I'm having firm oh HVAC in Mumbai and we are taking projects which consist supply and installation both part of work. suppose my project site running in Delhi where I have purchase some material and installed and I inform to supplier that billing address should be Mumbai and shipping address will be Delhi itself so in that case what will be place of supply and what GST to be charged (C & S or I GST ) ???
plz reply

regards
Samir Shaikh.