RTT delay = 24.2 micro sec
So , we need to calculate time taken to send 48 bit jamming signal ::
10*(10^6) bits -----> 1 sec.
48 bit -------------> 48/(10*10^6) = 4.8 micro sec
So , total time = (24.2 + 4.8 ) microsec = 29 microsec.
Min frame size is the data to be sent in 29 microsec = 29*10^-6 * 10 * 10^6 = 290 bits