Adrian is contemplating purchasing for $60,000$ a machine which he will use to produce $10,000$ disks per annum for five years. These disks will be sold for $9$ each and unit variable costs are expected to be $5.$ Incremental fixed costs will be $14,000$ per annum for production costs and $5,000$ per annum for selling and administration costs. Adrian has a rate of time preference of $10\%$ per annum.

By how many units must the estimate of production and sales volume fall for the project to be regarded as not worth while?

A $575$

B $1,293$

C $1,623$

D $2,463$