An LTI system with unit sample response
$$h\left( n \right) = 5\delta \left[ n \right] - 7\delta \left[ {n - 1} \right] + 7\delta \left[ {n - 3} \right] - 5\delta \left[ {n - 4} \right]$$ is a

The signal x(t) = $$\sin \,(14000\,\pi t)$$, where t is in seconds, is sampled at a rate of 9000 samples per second. The sampled signal is the input to an ideal lowpass filter with frequency response H(f) as following: $$H(f) = \left\{ {\matrix{ {1,} & {\left| f \right| \le \,12\,kHz} \cr {0,} & {\left| f \right| > \,12\,kHz} \cr } } \right.$$

What is the number of sinusoids in the output and their frequency inkHz?

The ninth and the tenth of this month are Monday and Tuesday _______.

It is ____ to read this year’s textbook _____ the last year’s.