Classify the following system (input x(t), output y(t), impulse response h(t)) as: time-varying or time invariant, casua

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Classify the following system (input x(t), output y(t), impulse
response h(t)) as: time-varying or time invariant, casual or
non-casual, memoryless or non-zero memory. (N.B. u(t) is the
heave-step function.)
3.1.1 𝑦(𝑡) = 3.5𝑥(𝑡). (3)
3.1.2 𝑦(𝑡) = 1.5𝑥(𝑡 − 1.1). (3)
3.1.3 𝑦(𝑡) = [1.5𝑥(𝑡 − 1.1)] + 0.01. (3)
3.1.4 𝑦(𝑡) = 2.5𝑥(𝑡)𝑐𝑜𝑠(2𝜋100𝑡). (3)
3.1.5 𝑦(𝑡) = 3.1𝑥(𝑡) + 𝑦(𝑡 − 1).