Jessica is selling books during the summer to earn money for college. she earns a commission on each shelf but has to pay her own expenses. after a month of driving from neighborhood to neighborhood and walking door-to-door she figures out that her weekly earnings are approximately a linear function of the number of door she knocks on she writes the equation of function like this: e(x)=7x-25 where x is the number of doors she knocks on during the week and e(x) is it her earnings for the week of dollars. what does the slope of jessica's function represent