please show all steps with good explanation . thank you

4. In a mass spectrum, what m/z value would correspond to the following fragment? H3C H 5. What compound has a significant m/z 70 in its mass spectrum? a. 1-pentanol b. 2-butanol C. Diethyl ether d. Octane e. (E)-2-pentene 6. The following MS belongs to an unknown compound. When analyzed using IR spectroscopy this compound displays a sharp, large peak around 1750 cm 1. Using this information, suggest a likely identity of this compound and explain your reasoning. 100- MS-NU-0033 80 60 Relative Intensity 40 20 o frontmpetitie mutta 125 25 50 100 75 m/z