Common difference between the fractions 4/10 13/20 9/10 23/20 14/10

Autility company burns coal to generate electricity. the cost c(p), (in dollars) of removing p percent of the some stack pollutants is given by c(p)= 85000p/100-p a) find the cost to remove 30% of the pollutant b) find where the function is undefined

Can someone me my sister? she is in third grade. 50 points and brainlist! ones that are not answered. plz and thx!

Does the problem involve permutations or? combinations? do not solve. the matching section of an exam has 4 questions and 7 possible answers. in how many different ways can a student answer the 4 ? questions, if none of the answer choices can be? repeated?