Given the signal e(t) = 3sin 4t + 2sin7t.

(a) List all frequencies less than ω = 50 rad/s that are present in e(t) .

(b) The signal e(t) is sampled at the frequency ω_s = 22 rad/s . List all frequencies present in e*(t) that are less than ω = 50 rad/s .

(c) The signal e ∗ (t) is applied to a zero-order hold. List all frequencies present in the hold output that are less than ω = 50 rad/s .

(d) Repeat part (c) For e ∗ (t) applied to a first-order hold.