Converting Units · Superchallenge problem

A delivery company charges $\$3$ for every kilogram or part of a kilogram that a parcel weighs (so a $1.2$ kg parcel costs the same as a $2$ kg parcel). Ana has four packages weighing $2.3$ kg, $1.4$ kg, $800$ g and $650$ g. How many dollars does she save by packing all four into one parcel (ignore the weight of the wrapping) instead of sending four parcels?