Economics homework help. Assume all systems below are real and causal. PROBLEM 1:Attachment 1Attachment 2Attachment 3The DC gain of an LTI System is de?ned as the value of the (constant) output yea) produced bythe constant input 936(t) = 1. The knee frequency of a ?lter is the frequency at which the power(not amplitude) of the transfer function drops by one-half from the pass band. For the simple ?lters we consider, we can use the de?nitions IH (jwkneenz = é|H(U)|2 for a lowpass ?lter, and1IH (jwknee) ‘2 = lim |H(jcu)l|2 for a highpass ?lter. Lil$00 Note: you may see knee frequencies de?ned as where the power drops by 3 decibels (dB). DecibelsP signal. The 3 dB are 10 log 10 of signal power relative to a reference power, dB = lOlogm ( Pref rule is chosen because 10 logm (1/2) a 3.