What gates and control would need to be added to the 4-bit adder to allow it to operate with two’s complement arithmetic to perform addition or subtraction? What changes will be required at the input and how can you select addition or subtraction as a function? Can you detect overflow of the 4-bit number using a single gate, if so, which gate and which signals?

i would first let him be aware that a cover letter is official and confidential and it requires a proper formatting so that the employer doesn't have hard time when going through it. he should write it in paragraphs of about two to four sentences and use proper grammar a , spelling and proper punctuation. i will also advice him not to be emotional and not also to use images.then base his attention to the details of the job described and not other things. that is he be specific to the responsibilities and to the employers requirements. on this he should make sure that the letter reflects how good he is for the requirements detailed by the employer

the letter should not be too long nor too short.