Free Space Path Loss

A synchronous orbit satellite communication system consists of a ground station with an antenna of gain $G_1=54$dBi and a satellite with an antenna of gain $G_2=36$dBi. The distance between the ground station and the satellite is $37,132km.$ The uplink frequency $($when the ground station transmits to the satellite$)$ is $f=14GHz.$ The downlink frequency $($when the satellite transmits to the ground station$)$ is $f=12GHz.$ Assume the gains of the antennas remain the same for both frequencies.

a$)$ Determine the minimum transmit power of the ground station necessary for the received power at the satellite to be greater than $-85$ dBW

b$)$ Determine the satellite's minimum transmit power necessary for the ground station's received power togreater than $-94$ dBW $.$ why do we supstitute in equations by uplink frequency and not downlink frequency??

c$)$ Why would a link designer choose the down$-$link frequency to be smaller than the uplink?