Check my answer? with precalc ?

the total cost (in dollars) of manufacturing scented candles is given by the function c(b) = 250+ 3b, where b is the number of candles manufactured. which function represents the average manufacturing cost, a, in terms od b?

a. a(b)= b/250+3b
b. a(b)= 250+3b/b
c. a(b)= (250+3b) * (b)
d. a(b)= 250+4b

i think it is either b or c. can someone tell me which it is and why?

Empty box + box + empty box fill in the box is equal to 30 how

Give the equations of two different lines that are perpendicular to the line 3x + 4y = 7.

Suppose that 3% of all athletes are using the endurance-enhancing hormone epo (you should be able to simply compute the percentage of all athletes that are not using epo). for our purposes, a “positive” test result is one that indicates presence of epo in an athlete’s bloodstream. the probability of a positive result, given the presence of epo is .99. the probability of a negative result, when epo is not present, is .90. what is the probability that a randomly selected athlete tests positive for epo? 0.0297