A and B workings please.

a) A manufacturer's marginal cost (MC) flmction is given by: 1000 1/3Q+12 MC: Find the equation of the total cost function if total costs are 5200 when Q = 8. b) A population of size x is decreasing according to the law dx x (it 250 where t denotes the time in days. If initially the population is of size x0 (that is, when t = 0, x = x0) find how long it takes for the size of the population to be halved