Dose every number have a reciprocal

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

An arc subtends a central angle measuring 7pi/4 radians what fraction of the circumference is this arc?

Witch represents the inverse of the function f(x)=1/4x-12