Answer = 4 batches of peanut butter cookies and 6 batches of chocolate chip cookies.
9/10 = 90/100, so 90/100 (which is 9/10)+ 9/100 = 99/100
3 is the lesser and 4 is the higher, because taking away 1 from four is 25%.
Choice (A) has zero slope becsuse her cost doesn't depend on the number of visits.
1.60/20 =0.08
0.08 per pen
