Please give explanations to answers, thank you!

Question # 10 A communication receiver has NF 20 dB and its RF bandwidth is 1 MHz. Suppose a preamplifier is placed at it:s input. Assuming that the preamplifier has again of 24 dB and a NF equal to 5 dB, determine the sensitivity of the system with the inclusion of the preamplifier. Hint: Use Friis formula: Answer hints: NF(Total) = 5.5 dB)