Simplify the expression
-4x2(3x − 7).

a. -12x3 + 28
b. -12x3 + 28x2
c. -12x3 − 28
d. -12x3 − 28x2

Jabari is power washing houses for a summer job. for every job, he charges an initial fee plus $30 for each hour of work. his total fee for a 4 -hour job, for instance, is $170 . jabari's total fee,f, for a single job is a function of the number,t, of hours it takes him to complete the job. write the function's formula.